If you are getting Error 85010020 when you try to sync your Google account on your Windows Phone 8 smartphone, here’s the deal.
Windows Phone was originally designed to use Google Sync AKA Exchange ActiveSync (or EAS) to sync Google email, contacts, and calendars. Google discontinued support for Google Sync for new customers on December 31, 2013.
To get rid of this error, you need to update your Windows Phone to Windows Phone 8.1, as the new Google protocols have been implemented from that version onwards.
On your Windows Phone, swipe left to your app list, tap Settings, scroll down to find and tap Phone Update, then the Check for update button. Your phone will connect to the server and tell you if any update is available. If available, run the update/s.
Once your phone runs Windows Phone 8.1, you will have no problem synchronising your Google account.