This is usually a network or connectivity error with google. From the logs - you are not getting an access token back from the google service. This could be a network issue or it could be a credentials issue or there could be a problem with your google account.
Unfortunately - I cannot help. You will just have to work through the problem. I’d suggest first rebooting routers, your vera and etc to clear any connection problems. Then re-enter your calendar id and credentials file. Also check your google console and see if your account has issues.
Bottom line - something has changed. If you remember doing anything then that would be a good place to start looking