Clients not updating Defs from GUP

I have some new GUPs on 12.1.4013.4013.

For testing we have set the Heartbeat/Download intervals to 5 min / 5 min.

The few clients we have pointing to the GUP have not updated their definitions and have been reporting back to the GUP consistently for several hours.

The SEPM is updating the check-in time, but the clients are not getting the latest definitions from the GUPs.

What can we do to force the clients to get definitions from the GUP?