Hi, an error message when trying to authenticate Google Analytics, states:
401. That’s an error.
The OAuth client was deleted.
That’s all we know.
This appears to be on Google's side but looks like something you need to check into. I searched the web for an answer and saw this answer, but don't know if it helps any:
"It looks like your OAuth client on the console (https://console.developers.google.com/) got deleted. You need to restore (if possible) or re-create it."
Customer support service by UserEcho