On the Administration | Hub Settings page provide the Hub URL of the following format
Сlick Register TeamCity service in Hub. >
Note that the Guest user in Hub needs to be allowed (unbanned) for the TeamCity service registration in Hub.
You will be redirected to the Services page in Hub. Verify the TeamCity Hub service using the Trust button.
After you trust the TeamCity service in Hub, return to the TeamCity Web interface to configure user synchronization.