Android app not logging in any more

?
Which application is it?
There are no Android applications made by Steamgifts.
(There are some that appear to be made by third parties, but there is no guarantee of their safety.)

Are these two things that you might be using that were created by a third party in the discussion?
SteamGifts for Android
https://www.steamgifts.com/discussion/Zpeq5/steamgifts-for-android
SteamGifts-iOS
https://www.steamgifts.com/discussion/za8KL/steamgifts-ios
The former appears to have closed about nine months ago.
The latter appears to have been created only recently.

As a general rule, it would be more correct to include links to the app store pages in the application's configuration information.
If cookie information or any data is corrupted, you will probably have to uninstall and try to reintroduce the application.
On a more indirect note, there have been times when Steam logins have been sluggish over the last few days due to Chinese New Year. Hopefully your problem is temporary.

PS　The category Help is more responsive.

The app actually still is maintained, though rarely gets an update. You might want to check if you have the most recent version.

Edit: Just in case that you maybe ignored the last update for the past two years. 😉

There are currently huge issues with the Steam log in. It appears that no one (or rather there are a huge lot of people reporting it) is able to log into Steam any more from the client and there's an error preventing any game to start.
I would check again in a few hours when Valve fixes it.

ok, tried again and now it works. all was due to Steam's own login issues. thankfully I'll keep using the Android app!