This service is very unreliable. One time it works the next it just sits and won’t open.
You need to provide more than a complaint. How about telling us what equipment you are using.
Have you tried to restart?
I have the same problem. The Tablo app will not open ( somewhat intermittent) unless the firestick is power cycled. This is the 4K Max Firestick. The previous generation did the same thing so it is not a Max problem.
What do you mean when you say that the app will not open?