Actually, I tried just a Google Project with only the Calendar API and grant.expired was received. I doubt that could be the issue.
Have you tried your personal account using the configured Google project? I suspect there is a restriction or limitation on the work account. 
I am actually doing this, i am setting a personal account to test and try to reproduce the issue, and i have a question : in our work account we added the support@nylas.com but only with reader role, not as an owner as the documentation says, do you think that can be the cause?
UPDATE:
I finally found the main cause, it was caused by a missing scopes in the google OAuth consent screen config (userinfo.email, userinfo.profile,openid ) and it works for me now, i received the grant.invalid webhook event, but is it normal to receive it with a 1 hour delay ? i revoked the accès at 9h45 AM and i received the webhook event at 11h04 AM .
Glad you were able to find the root cause!
There will be a small delay is pub/sub is not enabled - but it would not be an hour. Are other web hooks similarly delayed?
Hi @ram , no i don’t have any problem with the other webhooks
@saissaoui - let me pass this onto the Eng team, will follow up if any questions. I cannot reproduce the delay, but will see if we have any logging about this.
@saissaoui one follow up question, for grant.expired webhook would you happen to know the webhook_delivery_attempt value when received after an hour period? I assume it would be 1:
@ram I finally found the solution, it was another config issue, according to this article it’s an issue when we activate only calendar scope, so in the google connector params in the dashboard i went from this :
To this :
And it solved my delay problem
Thanks for sharing this @saissaoui - will set this as the accepted solution to ensure other’s are kept in the loop of this potential webhook delay.