Hello,
I have ProgTV installed on a FireTV and it works perfectly, but when I want to record to a folder from USB connected to the FireTV I get the error: Recording error! There are no recording permissions. Try selecting another folder for recording
I try with different folders and always the same error and the app have write permissions.
What could be the problem?-

Regards.
Oscar.

You can try some sub folder in Downloads. Also you can try ProgTV+ from site.

ps: In modern Android too many access limits