I'm trying to utilise a vRO workflow as a resource action in v8.1 (patch 2). The workflow has 2 inputs, first is type VC:VirtualMachine, the second is a string that's populated via a drop-down that calls an action passing in the previously selected VM. This approach is working fine when the workflow is run directly in vRO. Workflow config here:

I now need to get this workflow to work as a custom resource action. I'm following the logic used here to create the resource action: https://blogs.vmware.com/management/2020/08/introducing-custom-resources-and-resource-actions-in-vrealize-automation.html
So I've created the action to get the VC:VirtualMachine my name, tested in isolation it works fine, then I've configured my resource action:

When selecting a deployment the resource action appears as expected. When I run it I get:

So basically the action that is called to populate the protection plan dropdown is not being supplied with the selected VM, which it requires to function.
I checked out "Edit Request Parameters" for the resource action, and can see the ognl command that is failing

So my question is how do I get the VM to be passed into the action? I've spent quite some time looking at this and can't see anything obvious, any help would be appreciated!
Thanks!
Tim.