If your Android phone shows "null or unknown IMEI" or displays "not registered on network" errors, your device can't make calls, send texts, or connect to mobile data. The IMEI (International Mobile Equipment Identity) is a unique 15-digit number that identifies your phone on the carrier network. When it gets corrupted or unreadable, your phone essentially becomes invisible to cell towers.
You can check your IMEI by opening your phone dialer and entering *#06#. If you see "IMEI Null" or "000000" instead of a proper number, your device needs attention. Before jumping into advanced repairs, try these fixes in order. Many of them resolve the "not registered on network" error without needing to touch the IMEI at all.
Restart Your Phone
A simple restart is always worth trying first. When your phone powers back on, it goes through a fresh network registration process with nearby cell towers. This clears out temporary software glitches that may have caused the error. Hold the power button, tap Restart, and wait for your phone to fully boot before checking if the issue is gone.
Toggle Airplane Mode On and Off
Turning on Airplane Mode kills all wireless connections, including your cellular radio. When you switch it back off, your phone reconnects to the network from scratch. Swipe down to open your notification shade, tap the Airplane Mode icon, wait about 10 seconds, then tap it again to turn it off. This forces a fresh handshake with your carrier without needing a full reboot.
Remove and Reinsert Your SIM Card
A poorly seated SIM card can cause network registration failures. Power off your phone, eject the SIM tray using the pin tool that came with your device, and carefully remove the SIM card. Blow gently on the SIM and the tray slot to clear any dust, then place the SIM back in and push the tray firmly into place. Power your phone back on and see if it connects to the network.
Check Your Carrier Plan Status
Sometimes the problem has nothing to do with your phone at all. An expired prepaid plan, an unpaid bill, or a suspended account will show the same "not registered on network" error. Log into your carrier's app or website, or call their customer service line from another phone. Confirm that your account is active and in good standing before moving on to more technical fixes.
Reset Network Settings
Resetting your network settings wipes all saved Wi-Fi passwords, Bluetooth pairings, and cellular configurations. It sounds drastic, but it clears out corrupted settings that might be blocking network registration. Go to Settings > General Management > Reset > Reset Network Settings (the exact path varies by phone brand). Your phone will restart and attempt a clean connection to your carrier.
Change the Network Type Manually
Your phone might be trying to connect to a network band that isn't available in your area. Switching from 5G to LTE, or from LTE to 3G, can sometimes fix registration issues. Head to Settings > Connections > Mobile Networks > Network Mode and try selecting a different option like LTE/3G/2G. If your phone connects on a lower band, the problem may be with 5G or LTE coverage in your location.
Update Your Phone Software
Phone manufacturers and carriers regularly push software updates that fix network registration bugs. An outdated system can have known issues that have already been patched. Go to Settings > Software Update (or Settings > System > System Update) and check for any available updates. Install them, let your phone restart, and test the connection again.
Clear the Phone App Cache
The Phone app handles your device's telephony functions, including network registration. A corrupted cache in this app can cause all sorts of connectivity problems. Go to Settings > Apps > Phone > Storage and tap Clear Cache. This won't delete any contacts or call history. It just removes temporary files that may have become corrupted. Restart your phone afterward to let everything rebuild cleanly.
Try a Different SIM Card
If none of the above fixes have worked, your SIM card itself might be damaged. Borrow a working SIM from a friend or family member and insert it into your phone. If the borrowed SIM connects to the network without issues, your original SIM card is the problem and you should request a replacement from your carrier. If the borrowed SIM also fails, the issue is with your phone's hardware or software.
Factory Reset as a Last Resort
A factory reset erases everything on your phone and returns it to its original state. This is the nuclear option, so back up your photos, contacts, and important files first. Go to Settings > General Management > Reset > Factory Data Reset and follow the prompts. After the reset, set up your phone from scratch and check if the network error is resolved. If the problem persists even after a factory reset, your phone likely has a hardware issue with its radio module, and you should take it to a repair shop or contact the manufacturer.
