What to do when play store tells "Authentication required you need to sign in with your google account" And then I sign up but still the same I can't install apps.
This is a common problem and is often solved with little work.
This should fix your problem:
1) Remove your Google Account (From you device settings)
2) Clear Google-Play-Store cache and data
3) Sign-in with your Google Account again
4) Try to download an app