How to start an ATX power supply?

Question

Power Supply

There is an Enhance ENP-2220A power supply that I want to use to power the imax analog charger. The connector is 20 pin.
When you try to turn it on by closing the green contact (pc-on) and any of the ground - it does not react in any way. And if you close this green contact with white (-5V) or blue (-12v), then it turns on, but only while the circuit is closed.
What can happen to him?

Answer 1

While waiting for answers, I continued to search on other forums and found a dubious answer that it would not turn on without load, such as protection. I checked and it's true - if you connect the charger, then the unit starts with classic contacts, but no load. So, in fact, the issue was solved by myself)

Answer 2

it turns on, but only while the circuit is closed.

That's the way it should be. Close and forward, only I would also check with a multimeter that the voltage is within normal limits.