This KB provides information how distsrv probe works with licenses.
Release:UIM using physical licenses
Any probe requiring a license will be checked against a valid license.
If the hub under which that probe exists, does not have a distsrv, the license check will crawl to other hub(s) until it finds a hub with a distsrv probe.
If the local hub to which the robot with licensed probe is attached has the distsrv, then the license query will be checked and satisfied locally - irrespective of its failure or success.
If the local distsrv does not have a valid license, then the license query will not go any further and the probe will be stopped by controller.
So, in multi-hub scenarios, there are two options:
One distsrv, normally on the primary hub.
If distsrv resides on each hub, then you will need to add a Forwarding record on the main hub for Licenses so that licenses will be synced to all hubs and all license queries will be satisfied locally on each remote hub.
Robot licenses are different - they are applied manually and on the hub.