Authentication Required 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