When I press the power on button (applies to both the one on the mainboard(!) aswell as the one on the case), nothing happens, neither shutdown, when on, nor startup, when off.
The only way I can start it is by pressing direct key, after which the PC will power on and then restart multiple times. Powering off only works by pressing shutdown in Windows. The PC worked before in this configuration.
Does this mean that something on the mainboard is damaged? Or are there other possible reasons for this behavior?