Read the statement by Michael Teeuw here.
UNSOLVED MMM-GoogleTasks invalid_grant
My GoogleTasks module stopped working: it’s loading indefinetely. It did work in the past.
I thought maybe something is wrong with the authorization. So I ran “node authenticate.js” and got the error:
“The API returned and error: Error: invalid_grant”
I tried to download a new credentials file but the still got the same error.
What can I do?
Ive had a similar module. If it has a tokens file, or is storing the tokens somewhere. You can try and delete that, and then run authorize again.