Xiaomi Cannot Register on O2 in Birmingham

Xiaomi Not Registered on Network on O2 UK? (2026 Fix)

If your Xiaomi, Redmi or POCO phone shows "Not Registered on Network", "Emergency Calls Only", or fails to connect to O2 UK entirely, you're not alone. This issue can affect both physical SIMs and eSIMs, especially on imported or older Xiaomi devices. This guide covers the most common fixes for O2 UK and O2 MVNOs like Giffgaff, Tesco Mobile, Sky Mobile and Lyca Mobile.

Works For

  • ✔ Xiaomi 12 / 13 / 14 / 15 series
  • ✔ Redmi Note 12 / 13 / 14 series
  • ✔ POCO F / X series
  • ✔ HyperOS
  • ✔ MIUI 12.5+
  • ✔ O2 UK
  • ✔ Giffgaff (O2 network)
  • ✔ Tesco Mobile (O2 network)
  • ✔ Sky Mobile (O2 network)
  • ✔ Lyca Mobile (O2 network)

Note: MVNOs like Giffgaff, Tesco Mobile, Sky Mobile and Lyca Mobile run on the O2 UK network. The same fixes apply. Menu names may vary between HyperOS and MIUI versions.

Before You Start – Quick Checks

  • ✔ Restart your phone – Clears temporary software glitches.
  • ✔ Toggle Airplane Mode – Turn on for 30 seconds, then off.
  • ✔ Reinsert your SIM card – Power off, remove, clean contacts, and reinsert firmly.
  • ✔ Check for O2 UK outage – Visit the O2 network status page or call 202.
  • ✔ Check your account status – Ensure your account is active and paid.

If these quick checks don't work, continue with the step-by-step guide below.

Quick Navigation

Xiaomi Not Registered on O2 UK? Quick Fix

  • ✔ Select network manually – Settings → SIM cards & mobile networks → Network operators → Turn off "Choose automatically" → Select O2 UK.
  • ✔ Check IMS registration – Dial *#*#4636#*#* and check if IMS shows "Registered".
  • ✔ Enable VoLTE first – Settings → SIM cards & mobile networks → Your SIM → Enable "Use VoLTE" or "4G Calling".
  • ✔ Check Preferred Network Type – Try 4G (LTE) preferred instead of 5G.
  • ✔ Reset APN settings – Settings → SIM cards & mobile networks → Access Point Names → Reset to default.
  • ✔ Check for blocked IMEI – Dial *#06# and verify your IMEI number is valid.

Understanding "Not Registered on Network" vs "No Service"

These two messages mean different things:

  • "No Service" – Your phone cannot detect any cellular network at all. The signal bar is empty with a cross.
  • "Not Registered on Network" – Your phone can detect the network but cannot register on it for normal service. The signal bar shows a network name or "Emergency Calls Only".

This guide is for "Not Registered on Network" – the phone sees O2 but can't connect properly.

Diagnostic Signs – What's Causing Your Registration Issue?

SymptomMost Likely CauseGo To
"Not Registered on Network" or "Emergency Calls Only"Network selection or IMS registration issueStep 1 / Step 2
Signal bars present but can't call or use dataAPN misconfiguration or VoLTE disabledStep 5 / Step 3
Phone shows 4G/5G icon but no internetAPN or network type issueStep 5 / Step 4
No signal at all, SIM not detectedSIM slot or hardware issueStep 10
Giffgaff SIM shows signal but no dataAPN issue specific to GiffgaffStep 5

When This Is a Carrier Issue

SymptomLikely Carrier Issue?
SIM works in other phones but not yoursNo – phone issue
SIM doesn't work in any phoneYes – contact O2
"Not Registered" only in one areaYes – coverage or outage
"Not Registered" everywhereLikely phone issue
Account inactive or unpaidYes – contact O2

Why Xiaomi Won't Register on O2 UK

Understanding why this happens helps you fix it correctly:

Network Selection Issues

  • Automatic network selection fails – Xiaomi devices sometimes struggle to automatically select the correct O2 UK network. Manually selecting the network often resolves this.
  • Dual-SIM conflicts – If you have two SIMs, the O2 SIM may not register unless it's set as the primary data SIM or the other SIM is disabled.

IMS Registration Issues

  • IMS not registered – IMS (IP Multimedia Subsystem) registration is required for VoLTE, VoWiFi, and proper network registration on modern UK networks. If IMS shows "Not Registered," your phone won't register fully on O2 UK.
  • VoLTE disabled – O2 UK requires VoLTE to be enabled for proper network registration on most Xiaomi devices.
  • Carrier profile mismatch – System updates can introduce carrier configuration mismatches that prevent network registration.

APN and Configuration Issues

  • APN misconfiguration – O2 UK and its MVNOs (Giffgaff, Tesco Mobile, etc.) require specific APN settings for data access. However, APN misconfiguration usually causes data issues, not network registration failure. Only try this step if you have signal but no data.

Hardware and IMEI Issues

  • Blocked IMEI – If the IMEI number is blocked (e.g., from a stolen phone or unpaid bills), the device won't register on any network.
  • SIM card damage – A damaged or faulty SIM can cause registration failures.

Why O2 Specifically?

If your Xiaomi works on EE, Vodafone or Three but not on O2 UK, the issue is often related to one of these factors:

  • O2's device certification process – O2 maintains a list of approved devices for network features. If your Xiaomi model isn't on the list
  • O2's MVNO APN variations – Giffgaff, Tesco Mobile, Sky Mobile and Lyca Mobile all use O2's network but have different APN settings. Using the wrong APN can cause data issues or registration problems.
  • Imported Xiaomi firmware – Chinese or Indian ROM versions may not include O2 UK's carrier configuration by default. A global or EEA ROM is recommended for full compatibility.
  • VoLTE dependency – O2 relies on VoLTE and IMS for network services. If VoLTE is disabled or IMS registration fails, the phone may show "Not Registered on Network".

Based on reports from UK Xiaomi users and O2 customers, manually selecting the network and checking IMS registration are the two most effective fixes for this issue.

Step-by-Step Fixes

Step 1: Select Network Manually

Why this matters: Xiaomi devices can struggle to automatically select the correct O2 UK network. Manually selecting the network forces the phone to register with O2 UK directly.

  1. Settings → SIM cards & mobile networks
  2. Tap your O2 SIM
  3. Tap Network operators or Choose network
  4. Turn off Choose automatically
  5. Wait for the phone to scan for networks
  6. Select O2 UK (if you see multiple, try each)
  7. If the selection fails, try again after a few seconds

When this won't help: If you still see "Not Registered on Network" after manual selection, move to Step 2.

Step 2: Check IMS Registration Status

Why this matters: IMS registration is required for network registration on modern UK networks. If IMS shows "Not Registered," your phone won't fully register on O2 UK.

  1. Open the Phone app
  2. Dial *#*#4636#*#* – note that this code may not work on all Xiaomi models
  3. Tap Phone information
  4. Look for IMS Service Status or IMS Registration
  5. It should show Registered. If it shows Not Registered, your phone can't register properly
  6. If IMS is not registered, try the VoWiFi carrier check code: dial *#*#869434#*#* and restart your phone

When this won't help: If IMS is already registered but you still can't register on O2, move to Step 3.

Step 3: Enable VoLTE (4G Calling) First

Why this matters: O2 UK requires VoLTE to be enabled for proper network registration on most Xiaomi devices. Without VoLTE, the phone may not register on the network.

  • Settings → SIM cards & mobile networks
  • Tap your O2 SIM
  • Look for "Use VoLTE" or "4G Calling"
  • Ensure it's toggled ON
  • Restart your phone and test

When this won't help: If VoLTE is already enabled or the option is greyed out, move to Step 4.

Step 4: Check Preferred Network Type

Why this matters: If your phone is set to 5G only, it may struggle to register in areas with poor 5G coverage. Switching to 4G (LTE) preferred often resolves this.

  • Settings → SIM cards & mobile networks
  • Tap your O2 SIM
  • Tap Preferred network type
  • Select 4G (LTE) preferred or 5G/LTE/3G/2G Auto
  • Restart your phone and test

When this won't help: If you're in a strong 5G area and other 5G devices work, move to Step 5.

Step 5: Reset APN Settings

Why this matters: Incorrect APN settings can prevent data access. O2 UK and its MVNOs require specific APN settings for data access. However, APN misconfiguration usually causes data issues, not network registration failure. Only try this step if you have signal but no data.

  1. Settings → SIM cards & mobile networks
  2. Tap your O2 SIM
  3. Tap Access Point Names (APN)
  4. Tap the menu icon (three dots) and select Reset to default
  5. If you see "No APN configured," create a new APN with the settings below

O2 UK and MVNO APN Settings

Note: APN settings can vary by plan and MVNO. The settings below are the most common. Check your carrier's official website for the latest settings.

Carrier / MVNOAPNUsernamePasswordAPN Type
O2 UKmobile.o2.co.ukmobilewebpassworddefault,supl,mms
Giffgaffgiffgaff.comgiffgaffpassworddefault,supl,mms
Tesco Mobiletesco.co.uktescowappassworddefault,supl,mms
Sky Mobiledata.skyLeave blankLeave blankdefault,supl,mms
Lyca Mobilelycamobile.uklycamobilelycamobiledefault,supl,mms

Save the APN, select it, restart your phone, and test.

When this won't help: If APN settings are correct but registration still fails, move to Step 6.

Step 6: Clear SIM Toolkit Cache

Why this matters: Corrupted SIM Toolkit data can interfere with network registration.

  1. Settings → Apps → Manage apps
  2. Find SIM Toolkit or Stk
  3. Tap Clear data and Clear cache
  4. Restart your phone and test

When this won't help: If clearing the SIM Toolkit cache doesn't help, move to Step 7.

Step 7: Check IMEI Status

Why this matters: If your IMEI is blocked, the phone won't register on any network. This can happen with stolen devices or phones with unpaid bills.

  • Open the Phone app
  • Dial *#06#
  • Check that both IMEI numbers appear correctly
  • If IMEI shows as "Unknown" or "0", the phone has a software or hardware issue
  • If IMEI appears but you suspect it's blocked, contact O2 UK to check

When this won't help: If IMEI is valid and shows correctly, move to Step 8.

Step 8: Reset Network Settings

Why this matters: This resets Wi-Fi, mobile data, and Bluetooth settings without deleting your personal data. It clears any corrupted network configurations that may be blocking registration.

  1. Settings → Connection & sharing (on HyperOS) or Settings → Additional settings → Backup & reset (on MIUI)
  2. Select Reset Wi-Fi, mobile & Bluetooth or Reset network settings
  3. Confirm the reset
  4. Restart your phone
  5. Reconnect to your mobile network

When this won't help: If resetting network settings doesn't work, move to Step 9.

Step 9: Check for HyperOS Updates

Why this matters: Software updates often include bug fixes and improvements that can address connectivity issues.

  1. Settings → About phone → Check for updates
  2. Install any available updates
  3. Restart your phone and test

When this won't help: If you're already on the latest version, move to Step 10.

Step 10: Test SIM in Another Phone

Why this matters: This helps identify if the issue is your phone or your SIM/carrier.

  • Insert your O2 SIM into another phone
  • If it works, the issue is with your Xiaomi device
  • If it doesn't work, the issue is with your SIM or carrier

When to Contact O2 UK or Xiaomi UK Support

Contact O2 UK if:

  • The SIM works in another phone but not yours
  • You've tried all steps above and still can't register
  • You suspect your IMEI is blocked
  • There's a known network issue in your area
  • You need a SIM replacement
  • Your account is inactive or unpaid

Contact Xiaomi UK Support if:

  • You've tried all steps above and still can't register
  • You've tested your SIM in another phone and it works
  • The issue persists across multiple SIM cards
  • You suspect a hardware fault with the cellular antenna or modem chip
  • IMEI shows as Unknown

Contact Information

  • O2 UK Support: Call 202 from your O2 phone or 0344 809 0202 from any phone | O2 Help Centre
  • Xiaomi UK Support: Xiaomi UK Support Portal
  • Feedback app: Settings → Services & feedback
  • Xiaomi Community: Post in official Xiaomi community forums, including UK-specific threads

Final Verdict

If your Xiaomi won't register on O2 UK, the most common cause is incorrect network selection, IMS registration failure, or APN misconfiguration. Start by manually selecting O2 UK in Network operators, then check IMS registration using *#*#4636#*#*. If IMS shows "Not Registered," enable VoLTE and try the VoWiFi carrier check code *#*#869434#*#*.

If you're using a Giffgaff, Tesco Mobile, Sky Mobile or Lyca Mobile SIM, double-check your APN settings as MVNOs often require different settings than O2's main network.

Quick summary:

  • "Not Registered on Network" → Select network manually; check IMS registration
  • Signal but no data → Reset APN settings; check APN type
  • No signal at all → Re-seat SIM; test in another phone; check IMEI
  • Dual SIM issues → Set O2 SIM as primary; remove second SIM temporarily
  • Giffgaff/Tesco/Sky/Lyca specific → Check MVNO APN settings

Frequently Asked Questions

Why does my Xiaomi say "Not Registered on Network" on O2 UK?

This usually means the phone can detect the network but cannot register on it for normal service. Common causes include: incorrect network selection, IMS registration failure, VoLTE disabled, or a blocked IMEI.

How do I manually select O2 UK on Xiaomi?

Go to Settings → SIM cards & mobile networks → Tap your SIM → Network operators → Turn off "Choose automatically" → Select O2 UK.

What is IMS registration on Xiaomi?

IMS (IP Multimedia Subsystem) registration is required for VoLTE, VoWiFi, and proper network registration on modern UK networks. Dial *#*#4636#*#* and check IMS Service Status – it should show "Registered".

Does O2 UK work on imported Xiaomi phones?

Yes, but you may need to manually configure APN settings and network selection. Imported phones sometimes have different carrier profiles that don't auto-configure for O2 UK. A global or EEA ROM is recommended.

Can a factory reset fix "Not Registered on Network"?

Factory reset can help if the issue is caused by corrupted system files or network profiles. However, it should be used as a last resort. Before trying a factory reset, try the steps in this guide first.

Does replacing the SIM card fix this?

Yes, if the issue is caused by a damaged or faulty SIM card. If you've tried all steps and your SIM works in another phone but not yours, the issue is with your Xiaomi device.

Why does my Xiaomi work on other networks but not O2?

O2 uses a different network configuration and device certification process. Different MVNOs on O2's network (Giffgaff, Tesco Mobile, Sky Mobile, Lyca Mobile) also have different APN settings that must be configured correctly.

What APN does Giffgaff need on Xiaomi?

Giffgaff requires APN giffgaff.com with username giffgaff and password password. APN type should be default,supl,mms.

Do these fixes work on UK Xiaomi devices?

Yes. This guide applies to Xiaomi, Redmi, and POCO devices sold in the UK. The steps are identical across UK models.

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