Windows Powershell Script produces Output Results : Not Defined when run from SAM

In your script, it looks like its getting caught at the exit 1. Exit 1 tells SAM to return down. When it returns as down you lose the ability to see a message or statistic. I've changed the final ELSE statement to below which should help narrow down the issue

else
{
  Write-Host "Message: MicrosoftDFS WMI Namespace does not exist on '$computer'. Run locally on a system with the Namespace, or provide computer parameter of that system to run remotely."
  Write-host "Statistic: 3"
  exit 3;
}

If it is getting caught here it will return as critical instead of down and should help you narrow down where the logic in your script might be failing if that is not the expected result.

Also, are you identifying the "$computer" variable? The script you are running is looking for it as the first arguement