No data indicates that data isn't collecting for a resource. Either the VM no longer exists in vCenter (vm-id) or the vCOps collector account doesn't have perms to access it.
Go to environment overview, sort by tag "VM ENTITY" and select NotExisting.. that'll give the list of resources that no longer exist in vCenter and/or it doesn't have access to anymore. This is typically how you go and clean out old resources once they've been deleted from vCenter.