The error may simply be a sign-in issue, which sometimes occurs when the Play Store is updated. The first trick is to go into your phone's main Settings menu and then Accounts & sync and simply remove the Google account that is getting the "authentication is required" error.
The first trick is to go into your phone's main Settings menu and then Accounts & sync and simply remove the Google account that is getting the "authentication is required" error. Once you've done this, you can re-add the account and it should work just fine.
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