Please follow the below steps:
1. Firstly, it is recommended that you check whether the phone has recently downloaded and installed a third-party application. The issue may be caused by the incompatibility of the software and the mobile phone. It is recommended that you try to uninstall it: Settings>Apps>See all apps>Find the third-party application>UNINSTALL.
2. Confirm whether the background is unable to respond due to multiple applications running at the same time. Try shutting down and restarting the mobile phone regularly.
3. If it is invalid, please back up the important data, and then restore the factory settings.
4. If the mobile phone can detect the latest version, update the mobile phone firmware version: Settings>System>System Update>Check for Update (please back up the data in the mobile phone before upgrading).
If the issue persists, contact the Nothing Support Team for further assistance.