I get lights and fans come on, but doesn't boot anymore (no display)

[prisma cove]

PC has been working fine until today. It restarted itself randomly earlier to do Windows Updates but kept failing and looping. It the salvaged itself and I signed back into it. 10 minutes later, everything froze and nothing was responding. I gave it like 30 minutes to see if it will come back to life, nothing. I held the power down to try and reboot it, but then it no longer boots.
I've tried:

• Cleaning it out in case dust or something was overheating it.
• full power cycle, no difference
• reseated the RAM, no difference
• reseated the GPU and removed cmos battery for 10 minutes, no difference
• tried plugging displays into motherboard hdmi/dp with the gpu disconnected, no difference

I tried looking for status lights on the board but I don't see any.
So fans work, cooler works, leds light up, keyboard lights up but pressing caps lock doesn't toggle the caps status light on the keyboard. No display.

Spec:

• MSI z790-s pro WiFi
• rtx4090 gpu
• i9-14900k cpu
• 64GB DDR5 Corsair DOMINATOR ram
• I think 1000w PSU?

As i say, it's been fine until today... just today it isn't happy and no matter what I try, no success yet. 🙁

Idk if this helps, but it was the updates that seemed to begin this chain of events with it breaking

[onyx gull]

Best thing to try when you get to something like this is to try and get the minimal build possible which should work, eliminate other factors

So I would suggest removing your GPU again and using integrated graphics - perhaps try removing your RAM and trying just 1 stick at a time, if one stick / slot is faulty it can cause issues

Annoyingly it seems like that motherboard doesn't have any debug LEDs. Do you have the buzzer installed which will beep to indicate any issues (little circular thing hanging from red/black wires, usually near the bottom)

[prisma cove]

Yeah, it does have a buzzer but it doesn't make any noise. I did try the strat with minimal setup but unfortunately came up with the same result.
I ended up kinda giving up on it and decided to buy a new PC last night. Hoping to fit the HDDs into the new one and figure out a way to recover stuff on the old nVME drive that isn't backed up on cloud.
Means I'll have spare RAM and a spare 4090 gpu to fall back on as I think those components are fine. Is most likely a mobo or psu issue on the one I'm having trouble with - even if I did replace the faulty part, I'd still likely have problems with iCUE components not being detected properly and the RAM being forced into an underclock state due to that also not registering an XMP profile despite being set one in BIOS.
Thinking that once I did have some money saved up again, I may try to revive it with a new mobo and psu to have it as a secondary pc setup, but for now went with the peace of mind option of just getting a full new system instead.