Android - Getting "Authentication is required" when trying to access the Play Store

This worked for me: System settings > Apps > "All" (tab at top) > Google Play Store

Then press buttons in order: "Force stop" and "Clear data"

Exit Settings. Start the Play Store. Press at the top left top open the menu options.. Verify you have the correct account selected.

I went to Settings -> Applications -> Manage applications -> All, chose the Market application in the list, and clicked on "Uninstall updates" button which appeared there. It gave me an old, but working, version of the market app. I hope it will update itself in the future and will continue to work properly.

Thanks to Matthew for inspiring me to look over there.

You have to remove all your accounts from your device and re-add them. Or, just re-sync your google accounts from the Accounts & sync menu.

Go the Settings > Accounts & sync > Click on your account then remove account.

I removed all of my accounts that I had at that time, hopefully you haven't forgotten your passwords for your account. After I had done this, I restarted the device.

When my device came back on, I clicked on my Google Play Store, from there I was asked to sign in my account.