Try a re-discovery:
Unassign all of the virtualization components in Storage Manager:
Go to Settings > Virtualization (Assign ESX hosts), select all clusters and unassign the agent(s) from them. Click the ESX tab and assign ALL ESX hosts to an agent. In your resources list (Settings > All Resources), filter by ESX host (VMware ESX) and delete every single one of them. This will force STM to retrieve a new hosts list from Vmware.
Locate the Virtual Center(s) in the resource list (Settings > All Resources), click the edit button, choose "Select a Poller for this device" from the Poller drop down, and save.
Purge the Virtualization module:
Go on to the server that hosts the agent monitoring the Virtual Center. Stop the STM agent process in the services menu (run >services.msc) Navigate to \Storage Manager Agent\systemic\mod.sys.virtual.Virtual_1.0\, and delete the data directory. Start the agent process back up. You will need to do this for every agent you have monitoring the Clusters/ESX hosts
Assign the agent(s) back to the Virtual Center:
In the STM GUI, find the virtual center in the resources list, assign the Poller back to it (edit window) and let it collect. Wait 15-20 minutes and assign the Clusters / ESX hosts back (Settings > Virtualization (Assign ESX hosts).
Give it a couple of hours to collect.
If, after performing the steps above, you are still not seeing data please submit a support ticket at www.solarwinds.com/support/ticket/