Hovering over CPU/memory usage on VM's under hosts dashboards shows either 'There is no data to display' or 'Some data is not available' on the pop-up.
The VM agent does not collect the metrics shown in that Popup, so there will not be any data.
That's the reason why the pop-ups for the VM's under host dashboard shows No data message when you hover over.
Also for Virtual machine view, vmExplorer dashboard is always recommended.
Please find the kb article below: