“Doesn’t turn on” can sadly be anything, but I’ve seen a couple times that this can be literally just down to a faulty power button wiring. In the unlikely event that it is, it’s a very easy workaround.

Look inside, and follow the cable(s) from the power button to the two pins on the motherboard. These two pins should be directly next to each other (and are often labelled on the board as PWR_BTN or similar) - gently remove the power button wires (and remember to put them back on the same way afterwards), then try shorting the two pins with anything metal, I usually use just a flat-head screwdriver.

I repeat, it’s not overly likely, but in case it is the power button itself that’s faulty, the computer should then turn on as if you pressed the power button. Otherwise, proceed per the other post.

This sounds like a power issue to me. Is it a desktop computer? You could check that all the cables from the PSU are correctly plugged into the motherboard/GPU. Another thing worth trying is taking the components (RAM sticks/GPU) one by one and try turning on the computer after every part you remove, that way you can isolate the problem to a particular component. If it still wont work, then the PSU might just be fried. The easiest way to test that is to try with a different PSU, if you happen to have one of those laying around… I guess a power meter of some kind would work too, but I don’t know how to go about that.

It might also be some other unexpected bullshit. I did have a similar issue recently. I swapped the PSU and everything and it STILL didn’t work. Turns out there it was caused by a piece of lint in the GPU port. I took out the GPU and blew some compressed air into the port and it seems to have done the trick. I didn’t even know that could happen.

If it’s not a desktop computer then I don’t know shit.

good luck comrade

Is the machine spirit distressed in some way?

I would hold a vigil and commune with the machine spirit, of course using the correct incense and unguents

Make sure to respect its anima by saying a prayer to the Omnissiah while making the sign of the cog before striking the ignition rune

First thing to test would be the power supply. Is this a prebuilt (e.g., Dell, HP, eMachines, etc.), or something that you or a friend assembled from parts?

If it’s something that you assembled from components, the power supply should have a standard pinout on the cable that powers the mainboard (this is the big-ass one with the huge connector). Assuming it’s standard ATX, you can unplug the PSU, preferably remove it from the case, and bridge the PS_ON pin on the connector to one of the ground pins (e.g., with a piece of wire or a paperclip) to force the PSU to turn on once it is plugged into the wall outlet and switched on.

Video demonstration here:
https://www.youtube.com/watch?v=XIDarSg2jqk

NOTE: If you do not have a standard ATX power supply, do not attempt this! The pinouts are different and you may damage the power supply or start a fire. If you aren’t comfortable working around high-amperage direct current electricity, you may want to have your computer-savvy friend do this one just so that the magic smoke doesn’t escape and take your home along with it.

Anyway, if the power supply works outside the case, it’s the mainboard. If you reassemble everything again and it suddenly works, it was a loose or improperly seated connector; I’ve had that bite me on PCI Express power connectors (video card) once or twice.

Er juuust in case did ya flip the switch on the back of the power supply? Sure it’s obvious but I have forgotten this before and freaked tf out before i remembered and i build computers as a hobby