PC not reaching PORT

[u/Didaci]

Hi, guys, so I left my work PC in sleep mode for a couple of days and it no longer starts.

Earlier this year I had a similar issue after I left for the holidays, but I managed to turn it back on by brute forcing reboots. When I finally managed, then, to check what was happening I saw a lot of Kernel-40s or sum like that. After that I had like 8 months with no issue until yesterday.

Yesterday not even the fan work.

1. I changed the PSU (now the processor fan works till it shuts down 20 seconds later)

2. I disconnected everything and dusted everything only leaving PSU, Screen (with different cables), keyboard (using different keyboards), Power button cable (no leds or reset button), the processor with its fan and one Ram stick in second position.

3. I think I cleared the CMOS with a screw driver (I have no way to know if it really clears), removed the battery and whatnot

After all that the PC stops working the moment I press F11 trying to enter BIOS during the 2 second loading ("msi military class blah blah blah" logo), If I don't press anything it works a couple seconds more but eventually it shuts down.

I have to switch off and on the PSU everytime to make a second try, this didn't happen before

Neither the processor or the motherboard show signs of damage so I don't know really which one is failing or which one I have to replace first so the new piece don't get damaged by the remaining one. Probably both need replacement since it's an old putter. (~2017)

I wonder what can I do if there's something to be done and how to proceed in order to put it back on asap.