The geocaching.com server is not validating my sign in.
My date/time are correct, I am a premium member & signed in.
The (Reset Sign In) is not available in settings.
I have tried the (Log Out) option, but when I re-open the app the same problem is there.
Any ideas?

Samsung S6 with the latest update is installed

Can you send any screenshots of what shows after trying to log in? Groundspeak does the validation of credentials so Geooh just sends to them and waits for an OK response.

When did you try to sign in? Heard their servers had some issues last night and weren't responding to any app or website requests.

Installed the App this morning.  Should it have logged in automatically?
There is no "log in" screen.

Hmmm, every time I see that it's because of a date time issue with Groundspeak. They give an login error so there is nothing that Geooh can do. Last person who showed that screen found out their phone clock was off and after correction they could log in.

Try to completely delete the app off your phone and reinstall, then try to login to see if that helps.

I just set the time on my phone to automatic & the app works.
Just a little detail makes a big difference.
Thank you for the help. 

Oh great news! I'm not sure why the time needs to be accurate, but apparently the authentication software wants that. Let me know of any other issues or suggestions.