The most common reason for this error is that Local Platform does not have the correct permissions granted via your Google Account.
Very rarely this can happen to an account that was previously authorized, but is more common if the correct permissions were not selected when connecting your Google account.
In order to correct this you will need to first remove the invalid authorization, then create a new one.
Go to https://myaccount.google.com and click Third-party apps & services
Then filter to "other account access"
Click Whitespark
Finally, select "delete all connections you have with Whitespark"
This will remove the authorization in your Google Account for Local Platform.
Next, go back to the Local Platform to connect your google account. Ensure that you allow all permissions.
Now you should be able to enable GBP Management.
If you still receive an error, reach out to [email protected]