Another strange one. Existing VM replications appear to be working based on "last sync completed" time stamps. However, setting up a new replications result in a status of "Not Active". Right-clicking on a VM and choosing "sychronize now" results in this error:
Call "HmsGroup.OnlineSync" for object "[some long GID]" on Server "[server name/IP]" failed. An unknown error has occurred.
I Googled the error and found this VMware communities forum thread:
SRM5 using vSphere replication, status shows 'not active'
Read through it but note that you shouldn't have to reboot everything like one poster did. I rebooted the VRMS server in the recovery site and replications started working for all VMs again. YMMV. This happened to me after having rebooted the vCenter server also at the recovery site.