Using vRO actions to populate request forms error

Hello All,

I would greatly appreciate some help please. I have created a vRO action that should give a user an option of which storage policy to apply to a VM at request, depending of if it is to be a dual site vm or a single site VM.

I have created a Property Group with 2 property defiinitions

Definition 1 -
AvailabilitySelector
Drop Down Box
PreDefined Values - Single Site / Multi Site

Definition 2 -
VirtualMachine.Disk0.StorageReservationPolicy
Label - Storage Policy
Data Type - String
Display Advice - Dropdown
External Values
Pointed to my vRO Action item

vRO Action Item
// High Avalability to storage selection
if(AvailabilitySelector)
{
 switch(AvailabilitySelector) {
  case "Dual Site":
   return ["3PAR FC"]
   break;
  case "Single Site":
   return ["3PAR NL"]
   break;
    };
  }
else {
 return ["Please Select availability"];
 };

Now when I go to request to catalog item I get an error:

Unable to refresh request form from the server System exception.

I get this error as soon as the request page loads, I can see the dropdown menu for site collector, but the Storage Profile dropdown never populates.

Any help here would be greatly appreciated, I am pretty stuck at the moment.

Thanks

Dean