Problem with T-Mobile Home Internet app

I've got an Arcadyan KVD21 5G Gateway from T-Mobile and used the T-Mobile Internet app to configure it. Everything is working, but when I try and launch the app on my phone, it flickers or a millisecond on the gateway home page, then goes to the initial screen (the one with the magenta "T") and I just get a spinning gear icon for as long as i leave it there.

I try killing the app, but when it's relaunched, the same thing happens. I deleted the app and then reinstalled it from the App Store, but the problem still persists.

The weird thing is that sometimes, like first thing in the morning, it connects with no problem. ¡Imagínense!

Is anyone else having this problem, and if so, have you solved it?

As always, thanks in advance for any insight.