You need to have writer access to sync appointments to the selected Google Calendar. Please check with the Google Calendar owner in case syncing is required.
For Group Calendar:
**For Unassigned Calendar:
**
Step 1: The owner of the Google Calendar needs to be logged into Google and go to calendar.google.com.
Step 2: Hover over the desired calendar, then click the three-dot icon and select "Settings and Sharing."
Step 3: Scroll down to "Share with specific people" > Click "Add People" and add the email address of the Google Account that is synced in the platform > Set the permissions to "Make changes to events" > Click Send to save.
The Google Calendar should now be in sync with the platform.