Did you find a solution to this? I'm having the same issue.
Nevermind, I think I found the answer. I had to re-import the SSL certificate for the PowerShell host... in doing so I realized I had two PowerShell hosts in vRO. After deleting one and running update on the other... apparently the one i deleted was the one associated with my Workflow. All I had to do was edit my workflow and reselect the PowerShell host.