Please try the below:
1. Check whether the battery optimisation function is turned on on the phone. If so, disable it: find the app icon on the screen, long-press it and go to App information > App battery usage > Manage battery usage > Optimise.
2. Check whether your mobile network is working properly. If not, restart your phone and change to a better network before running the app.
3. Ensure the phone is updated to the latest system version. If not, update and try again.
If the issue persists, contact our Customer Support for further assistance.