any other advice for at&T??? Bought a New Samsung a53 5g unlocked,And not At&t branded on amazon,And on powering up getting message>Connection problem or invalid MMI code has done this a couple times making calls...YES everything works,And tried all the fixes I could find online...And At&t suggest replacing sim card,But still no luck replacing the sim card either... live with the message or buy a att branded phone? I'm almost sure that's the issue,But hate to return,And buy again...it is on prepaid At&t,But the phone should be compatible...any real fixes Thanks
To troubleshoot and resolve connection problems or invalid MMI code issues, you can try the following steps: 1. Check for Network Issues: Temporary network connectivity problems can cause the error. Ensure you are in an area with good network coverage. 2. Verify MMI Code Entry: Make sure you are entering the MMI code correctly to avoid the error message. 3. Enable and Disable Airplane Mode: Refresh network connections by toggling Airplane mode on and off in your phone's settings. 4. Toggle Your SIM Off and On: Turn off and on your SIM card in the SIM manager settings to address network issues. 5. Enter the Code in Safe Mode: Test entering the code in safe mode to check for any third-party app interference. By following these steps, you can troubleshoot and resolve connection problems or invalid MMI code errors on your Android device.