Hardware Insights specializes in power supplies. In this part of the forum, you will find detailed information on every aspect of power supplies, including how to repair them and how to judge if a power supply is a good quality unit or not.
Connect it to the 12V output with the power supply powered off. When you turn it on, you should see a 12V spike as it powers on. If you can't see that, then it sounds like a contact issue.
One other thing you could try is changing the coupling setting. I can't remember off the top of my head whether it needs to be AC or DC (although I think it might be AC)