Desktop have no voltage

Hi Everyone,

My pc stops working.

I test my ATX with paperclip and voltage are good. Test switch: good. When I plug my24 pins on motherboard, I have wire, I have no voltage , I have only 5 volts on my Purple wire (standby).

I have my 3.3 volt at the switch pins, even short them nothing happen.

Where is the problem? How to find the solution ?