A. 1. Ensure the SIM card is properly inserted into your device. Power off your device, insert the SIM card, and then power it back on. 2. Check if the SIM card is activated. You can do this by inserting it into another compatible device. If it works there, the issue may be with your original device. 3. If the SIM card is still not working, try resetting your network settings. On most devices, this can be done by going to Settings > General Management > Reset > Reset Network Settings. 4. If none of these steps work, consider checking for any software updates for your device that may resolve compatibility issues.