1. Not wiped after brushing, double cleaning. Or there is no automatic double clearing after the online ota upgrade of the mobile phone, which leads to the confusion of the system cache, so the error is reported.

2. It is the confusion caused by using some synchronization tools to synchronize contacts, text messages, call records, photo albums, etc.

3. Information stored on 3. SIM card.

4. For example, the necessary apk of the system was deleted, or a different version of the apk was replaced, resulting in an error.

Universal solution:

1. Turn it off.

2. Take out the sim card.

3. Restart the machine without installing the sim card.

4. After restarting, enter Settings-More-Mobile Network-Network Operator.

5. Wait about 30 seconds after selecting, the network operator will appear, and then click Auto Select.

6. Turn it off.

7. Insert the sim card, restart and solve the problem.