When setting up the connection in UMC for the vCenter and NSX Manager you receive an error stating the two are not paired.
The given NSX Manager is not paired with the vCenter '<IP of vCenter>'. Check the NSX Manager details.
For cause 1:
If the vCenter and NSX Manager are not setup/paired together correctly, this must be fixed first.
If the vCenter and NSX Manager are configured correctly, make sure the account specified in the Connection configuration for VMWare vCenter Server and NSX Manager have administrator rights.
For causes 2 and 3:
Match the connection information in UMC with how the vCenter is registered with NSX.
For cause 4:
Restart the DCS Manager Services and UMC services.