Q. When I launch the Authenticator app, the screen locks and I can't operate it.
A. If a lock screen is set up on your smartphone, the Authenticator app's App Lock feature will be automatically enabled upon installation.
To unlock the Authenticator app, use the same method as your smartphone's lock screen.
If you do not wish to use the Authenticator app lock (screen lock), first unlock the app, then tap the "︙" icon in the top right corner, open "Settings", and turn off the "App Lock" option.
Reference: What is App Lock in Authenticator?