Message Queuing is going to be needed on the SnapCenter Server. The installation should have automatically installed it, but I have heard of a few cases where this didn't happen for some reason.
I'd certainly verify that message queuing is enabled on the SnapCenter Server as well as the plug-in host.
If that doesn't resolve the issue the best thing to do would be to open a support case.
They can gather the logs and triage the issue properly.
John