I am just dealing with this problem. I figured it out. I am assuming you connected at least once.
The problem I had was Google Home shows Hubitat as unlinked but it really isn't.
1. Go to https://myaccount.google.com/
2. Click on the security tab
3. Near the bottom find:
4. Find Hubitat and click on the unlink icon
5. Go back and do the normal Google connection steps.
Mine worked after that.
