Failed to authenticate with Google Just recently, I have been dealing with this frustrating problem of my apple mail not being able to authenticate my Google account. I tried different gmail accounts, removing and re-adding the accounts, rebooting my Mac etc. Still no use. 

Can someone guide me through the process of getting this issue fixed? It is super frustrating for me to not be able to check my email using Apple mail.
I had this same issue now, I think. I had updated the password for my gmail account and needed to re-authenticate the Google account in Mac OS. When I went into System Preferences > Internet Accounts I got a dialog saying I needed to re-authenticate and when I clicked the "Open Safari" button in the dialog I just got an error message saying Failed to authenticate with Google.

Solution was to restart my computer, after that it worked just fine.

(I also set my default browser to Safari as recommended on reddit but that didn't help before the restart so I don't think it helped at all)