The most common reasons when Google integration breaks

The Google connection expireS due to password change and some other reasons you can find here

Due to the connection issue, the main (refresh) token expires. In general, in an ideal situation, the refresh token from google was never intended to expire unless these are the reasons

You just need to reintegrate google-connection and all should be fine, it happens when google revokes our access token due to you or a user whose google account is connected changing their google password, or some change in google account.

Not just appointments, all other events/data also stay, and won’t be deleted unless the calendar is deleted, the re-integration never ever affects any existing GHL data except token refresh (oAuth).

We do not add the error banner for all the calendars, that will only be true of all the calendars with that google account synced to it and all should be fine when you reintegrate your google connection, Any of the synced appointments will not affect due to this.

How to fix it for an unassigned calendar: 

If you will remove the linked calendar from the GHL calendar with the trash icon next to where you add a synced google calendar, it will remove all non-GHL events, but in this case, you don’t need that, this is just for info. 

How to fix it for a Group calendar: