Directv app on Firestick not working

Have you tried a different device like a phone, tablet, or PC? Also, have you verified your account information on-line?

I don't have any problem streaming on other devices. What do you mean by "verifying my account?"

Verifying your subscription, etc.

Also, are you a new subscriber? If so, are you a previous DirecTV Satellite or AT&T subscriber using the same credentials (id and password)?

I have the Ultimate package. I've had service since February.

...and the other info? Previous subscriber to satellite or AT&T using same credentials?

We regret that you are having trouble utilizing the DIRECTV App on your Firestick device and encountering connectivity issues with your Gemini devices. These shouldn't be happening. We'll send you a DM to investigate further and address your other concerns. - Lorie, DIRECTV Community Specialist

The only other account that I've ever had is the ATT Fiber that we also started in February, which is the WiFi I have everything connected to. I don't have any problem using the app on my phone when it's connected to the WiFi.

So are the account credentials for the AT&T Internet the same as with DirecTV Stream?

If so, the first thing to do is to log in to your DirecTV Stream account and change your password. Restart your fire stick, and try again.