You need to ensure that the Xendesktop GUID for VMs matches the Hyper-V or Vmware GUID.
Vmware View GUIDs on Host Machine
get-childitem -path xdhyp:\hostingunits\hostservername -recurse | select -property name,id | Export-csv C:\host.csv
Xendesktop view GUID
Get-brokermachine -machinename uk\machinename | select Name,Hostedmachineid
If they are out sync, then you will need to set the GUID In Xendesktop to match the hypervisor with the following command
set-brokermachine -machinename domain\computername -hostedmachineid xxx-yyyy-zzzz
Note : If the command to get the ID from Vmware fails, it can also be gained by changing directory to cd XDHYP:\connections\hypervisorname then dir *.vm >out.txt and check inside the output for the machines ID