The app cannot be installed
Check if the "Install unknown apps" is enabled under "Settings-Apps & notification-Special app access-Install unknown apps", then select the App source, enable "Allow from this source".
1. Check if the format of App is apk. It is recommended to download the app from a trusted source.
2. Change try a different trusted source is possible. Please clear browser cache and download or install it again or try it later.
3. Please back up all the data, clear cache and flash to the latest OS version.
The app cannot be upgraded
Check if the phone and App has the permission to access network.
Check if the "Install unknown apps" is enabled under "Settings-Apps & notification-Special app access-Install unknown apps", then select the App source, enable "Allow from this source".
1. Please back up all the data, clear cache and flash to the latest OS version.
2. Check if the handset is restricted by third-party system management app, if yes, it is recommended to uninstall third-party app first.
3. Please clear cache, back up all the data and flash back to the official latest OS version.
App flashback
1. Check if the handset is in good network condition. Cross-check between wifi and mobile data if possible.
2. Try other trusted sources to download and install.
3. Cross-check if the app flashback issue also occurs in other brands mobile:
a.If yes, it is because of App compatibility issues. It is recommended to contact the third party app developer.
b.If the issue only exists in the OnePlus device, please enter into "Settings-Apps & notifications-See all apps", then select the App, tap "Storage-CLEAR STORAGE, CLEAR CACHE" to clear data and cache.
4. If the issue still persists according to the above steps, please uninstall and try to install again.
5. If the issue still persists, clear cache, back up all the data and flash to the official latest OS version.