Solutions:
1. Re-enable the data switch.
2. Replace the access point (NET/WAP), if no APN, resetting is possible.
3. Re-enable/close the flight mode attempt.
4. It is suggested to check whether there is any overdue fee.
5. Guide and check whether Internet works on mobile phone.
6. Guide and check whether surfing the Internet is disabled in traffic management.
7. Check whether the Internet is disabled for the third-party software.
8. Back up and empty the data. Don't restore the backup attempt.
9. It is recommended to try the latest system of line brush.
If none of the above methods can solve the problem, it is suggested to take mobile phones to the Xiaomi authorized after-sales center for inspection.