We have one PC with a PM800-M2 motherboard on which the front panel power button is a no-op. It will neither start nor stop the system. System boots fine when PSU rocker switch is moved to 0 and back to 1. PSU voltages are nominal according to the power monitor built in to the BIOS. System seems to operate fine otherwise.
I have ruled out the front panel. The button will reset the motherboard if connected to the reset jumpers. the reset button, which is also good, will not power up the system if connected to the power up jumpers.
The BIOS offers no option to ignore the power button. Closest option is to change its action when system is running from instant-off to 4-seconds-off. It's set for instant-off. Button does nothing even if held for 4 seconds.
Anything else I should try before I write it off as a broken motherboard or PSU?