The "The Cluster For the Resource Could Not be Found" error message is displayed while trying to remove an unused hosting unit using the Studio Console.
From the PowerShell, remove the existing cluster that is offline using the following command:
dir XDHyp:\HostingUnits
Delete the hosting unity using the following command:
remove-Item -path 'XDHYP:\HostingUnits\cluster'
Change it back to old name or use the new host connection.
This error might occur because of lack of permissions to the user account on the vSphere. The vCenter may not be able to find the vSphere host connected to the vCenter because of this.
Naming convention of the network in the host connection might got changed. Verify the same by creating a new host connection and comparing both connections with the command:
asnp Citrix*
dir XDHyp:\HostingUnits