If anyone struggles with the ADB permission granting on OnePlus devices. Follow below steps
Open developer options
Enable 'USB Debugging'
Scroll to the apps section in the developer options
Toggle 'Disable permission monitoring'
Restart the device (Important)
Now try granting permission via Poweramp web ADB tool or adb shell
Note
There's a bug in the Poweramp web ADB where it does not display any error message if user try to grant permission without enabling 'Disable permission monitoring'. If you try it in adb shell it throws a security exception as expected
