Eventually, Notifications stop sending to users and this is the error reported in the Audit History:
No notification sent to ‘user@gmail.com’ because no Notification Device Token is present for this user,
The support team will solve this issue for you after long days. The last time they solved it, I was prompted to give permission to the app with the google account. I don’t know how they did it.
I would like to know how to prompt users that don’t have the Notification Device Token to Sign in to Google and give app permission so they recover the device token.