Powershell – Method invocation failed while trying to create a pop up

If you're using Windows Server 2008 R2 then there is an x64 and x86 version of PowerShell both of which have to have their execution policies set. Did you set the execution policy on both hosts?

As an Administrator, you can set the execution policy by typing this into your PowerShell window:

Set-ExecutionPolicy RemoteSigned

For more information, see Using the Set-ExecutionPolicy Cmdlet.

When you are done, you can set the policy back to its default value with:

Set-ExecutionPolicy Restricted

You may see an error:

Access to the registry key
'HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\PowerShell\1\ShellIds\Microsoft.PowerShell' is denied. 
To change the execution policy for the default (LocalMachine) scope, 
  start Windows PowerShell with the "Run as administrator" option. 
To change the execution policy for the current user, 
  run "Set-ExecutionPolicy -Scope CurrentUser".

So you may need to run the command like this (as seen in comments):

Set-ExecutionPolicy RemoteSigned -Scope CurrentUser