Recently I was trying to add a Virtual Switch to a new Hyper V Server and I got an error similar to below

Although the Virtual Switch seemed to add ok , it was coming up with Errors in the Cluster Manager ( Status Unavailable ) 

The server was actually already added to the Failover Cluster Manager. And I noticed that the

“Microsoft vmm dhcpv4 server switch extension” filter was missing. This gets added to a Node on adding to cluster

Evicting the Hyper V host from the Cluster then deleting and re-adding the VSwitch Resolved this