The computer turns off 5 seconds after starting, the PSU is working, what is the reason?

Question

Iron

Last night I turned off the PC through the button in the start menu. It turned off normally, only after that it started to turn on and off itself after 4-5 seconds, without even loading the BIOS. Today I check - the same situation. PSU checked by the "paper clip" method works stably. Tried disconnecting everything, down to the CPU - nothing changes. Help, guys, how can I fix it and what could be the problem? The computer is new, the assembly is not even a month old. I have nothing to work on :/

Answer 1

Looks like the power button is stuck.