How to check app availability?

Question

Android

Hello
, Can you please tell me how to check the availability of the application?
I have an app that asks me to sign in.
I enter that info
. The app checks if it's currently
available. If it's available, it lets me sign in.
Tried to check through Walshark
But nothing is clear there, only ip addresses.
How can I check to make a permanent check?
Application availability.
Let's say he tells me that the application is available and I go there
Or Not available and notifies me about it.
Tell me please.