Why does the on/off button on the case only work once?

Question

Frame

Hello. There was a following problem.
The power button on the case (DeepCool Matrexx 55 Mesh 4F RGB) works only once, then it simply does not work.
What I did: turned off the power supply, turned on the power supply, pressed the button - the computer started up, pressed the button - the computer turned off, pressed the button - it does not turn on, turned off the power supply, turned on the power supply, pressed the button - the computer started up. And so in turn. What could be the problem?

Features:
Motherboard: Asus Tuf Gaming B450M-Pro S
Case: DeepCool Matrexx 55 Mesh 4F RGB
PSU: Chieftec Polaris PPS-750FC

Answer 1

There was a problem with the Power SW wire, the wire protruded from the "plastic nozzle".
Apparently the marriage of the body. Self inserted to the end and clamped. Earned.

Answer 2

Investigative experiment number 1.

pressed the button - the computer turned off, pressed the button - it does not turn on

In this place, disconnect the 24pin connector from the motherboard (without turning off the PSU), wait half a minute to be sure, plug the connector onto the board, and try to start it with the button.
Investigative experiment number 2.

pressed the button - the computer turned off, pressed the button - it does not turn on

In this place, we disconnect the 24pin connector from the motherboard (without turning off the PSU), with a multimeter in up to 20V mode, we watch the voltage between the black and purple (purple) wires on the 24pin connector. Should be about 5V. Next, we try to start the power supply using the folk method of a paper clip (we close the green and black wires with an unbent paper clip or any pro-thread).
If the PSU did not start with a paper clip or there are no on-duty 5V on the purple wire, the matter is clear, the PSU is in the trash (or repaired by a craftsman with a soldering iron).
If it starts up, then suspicions are not yet removed from the PSU, but the motherboard becomes the main suspect.

Answer 3

Perhaps in the settings of the operating system.

(such as this)