Can you check the power on switch on the case to see if it is working properly?
Nothing seems to be wrong with the switch!
I had an old old custom built machine using Antec chassis, with its own PSU. The pin test revealed that the front panel worked perfectly, the fans both on CPU and in PSU were spinning. However, when I connected power line instead of using the pin, to the MoBo the fans would not rotate and front panel became lifeless! Tried to laugh but choked.