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If you encounter this problem during use, you can refer to the following suggestions to troubleshoot:
1. Poor contact between the phone's SIM card and the SIM card slot ejector can result in a malfunction of the SIM card circuit. To resolve this, remove the SIM card, wipe it with a clean cloth, and reinstall it;
2. The SIM card can not be registered on the network. Insert the SIM card into another phone and check if it still shows no service. If it still shows no service, it is due to the SIM card. Please visit the service provider to register again;
3. If you are in a remote mountainous area where there are no nearby communication base stations or are outside the coverage range, it is normal for the phone to show no service. Try changing your location;
4. Unstable signals can occur when you are in high-speed moving conditions, such as on a bullet train, high-speed train, or airplane. This can lead to intermittent loss of signal, and the phone will restore service when you are not moving any longer;
5. Incompatibility between installed applications and the system can cause the modem in the phone's signal processing circuit to shut down. In such cases, try restarting the phone and uninstalling any suspicious applications installed before the issue occurs;
6. If the SIM card temporarily loses connection in an area with no network signal coverage, manually search for and register on the network again.
Please feel free to contact the after-sale service center if you need further assistance.