Internet Accounts app on Mac "Fails to Authenticate With Google". How do I remedy this?

I received an email yesterday saying that I had a WhatsAp message. When I replied to the sender (a friend) querying the message, emails were sent from my gmail account to a number of unknown destinations (not my address book). Google has today alerted me to the fact that someone has tried to use my password to get into my account - not me - and advised me to change my password, which I have done (on my android phone). I have subsequently tried to log into my Gmail account on my Mac but the Internet Accounts app (which says that OSX would like to view and manage my mail) tells me it "Failed To Authenticate With Google”. I do notice that the email address on the app is the old “googlemail” configuration rather than the newer “gmail” one.

How do i remedy this?