I’m using Oppo F9 and F11.
All permissions granted but still asking to update permission.
Clicking update permissions again does nothing.
https://forum.avast.com/index.php?action=dlattach;topic=224716.0;attach=205357;image
It is possible that the app is not able to initiate the setup of appropriate permission. Please try to setup the permission manually:
go to Device Settings > Security > Floating Windows - there you should be able to activate the permission for the Avast Mobile Security app
Once you do, you should be able to finish the Anti-Theft activation.