Hello! If your Oppo A83 is showing a null IMEI and no SIM card is detected, it could be due to a software issue or a problem with the hardware. Here are a few steps you can try to resolve the issue:
1. Restart your phone: Sometimes, a simple restart can fix minor glitches. Turn off your phone, remove the SIM card, wait for a few seconds, then reinsert the SIM card and turn on your device.
2. Check SIM card: Ensure that the SIM card is properly inserted into the SIM card slot. Try removing the SIM card and reinserting it to ensure a secure connection.
3. Update software: Check for any available software updates for your Oppo A83. Software updates often include bug fixes and improvements that could resolve issues with the IMEI and SIM card detection.
4. Reset network settings: Go to the Settings menu on your Oppo A83 and look for the "Backup & Reset" or "System" section. From there, select "Reset Network Settings" or a similar option. This will reset your network settings to their default values, which can help resolve connectivity issues.
5. Factory reset: If all else fails, you can try performing a factory reset on your Oppo A83. Keep in mind that a factory reset will erase all data on your phone, so make sure to back up any important files before proceeding. To perform a factory reset, go to the Settings menu, select "Backup & Reset" or "System," and choose "Factory Data Reset" or a similar option.
If none of the above steps resolve the issue, it is recommended to contact Oppo customer support or visit a service center for further assistance. They will be able to diagnose the problem and offer a solution specific to your device.