vSphere Replication server registration might take a long time depending on the number of hosts in the vCenter Server inventory.
Problem
If the vCenter Server inventory contains a few hundred or more hosts, the Register VR Server task takes more than a few minutes to complete.
Cause
vSphere Replication updates the SSL thumbprint registry of each host. The vCenter Server Events pane displays Host is configured for vSphere Replication for each host as the vSphere Replication server registration task progresses.