Apple TV app not working

Using Apple TV 4k (1st gen.), when trying to open TV app or sometimes AppStore as well, it is spinning for a while and give message "Apple TV app isn't available right now. Check your internet connection and try again". Internet (ethernet) connection is fine, as all other apps working properly.

Tried to reset and update - did not help.

Tried to remove & add user - did not help.

Tried to change Region (random one, same as billing address, else) - in 1 out of 10 attempts TV App starts working, after some time, stops working and shows same message (app isn't available...).

Once more symptom: Subscription is spinning under default user, and not responding to anything.

Please help, don't know why paying so much and do not get the service.