This question already has an answer here:
From this morning I cannot use anymore any account based on Gmail (neither work account). It asked me for password and every time I insert the correct one, it gives me a "grey" screen (check the screenshot below). I tried already to delete all the google/gmail entries on login/all from Keychain Access, to reboot my Macbook but the problem doesn't get solved. Anyone knows how to solve this? Thank you!
I created another thread because I cannot comment there (50 points needed and because the solution applied there is not working). As I said in the comment probably it was working only for an older version of OSX.