[SOLVED] Computer booted fine yesterday but today it won't display anything and Red CPU LED is lit ?

[Vikeo]

I bought some used pc parts, don't know how much they had been used but I think very little if at all, don't see anything that would indicate long time use at least.

These are the specs of it as of right now:
Amd Ryzen 5 3600
Msi B450M Mortar Max
Rx 590 (xfy)
2x 8gb HyperX Fury DDR4 2666hz
EVGA 650 GQ

I got the PC set up two days ago and could set up everything just fine. I installed all the latest drivers and flashed the latest bios update. I do think that I did flash the wrong bios (latest B450 Mortar Max bios, without the M) and I feel stupid for that.
When I was going to bed on day 1 the computer didn't fully turn off after I had pressed Shut Down in windows, which I thought was weird. I could shut it down by holding the power switch though. The next day it started fine, but when I turned it off it still didn't fully turn off, and holding the power switch didn't work. I wanted it to turn off fully so I turned off the power supply.

This morning the computer "turns on" but doesn't display anything. The CPU EzDebug LED is lit and I didn't know what to do.

Now I've done everything in the "no POST" guide except fro breadboarding.

I've also tried flashing the correct BIOS update, but I don't know if it did anything. I followed a guide that said that a red LED flashes when it's flashing the bios and stops when it's done, and the LED turned off. After a couple minutes the LED just becomes solid in my case though, so I don't know if it's done or not.

I've reseated the CPU a couple times, no bent pins. I don't know if there can be anything in the "pin-holes" that can cause this, but I can't see/find anything out of the ordinary in regards to the CPU stuff.

I tried using another PSU (Corsair RM750) but it's the same as the other PSU.

That's about it. After everything I've tried I still don't know the cause of the EzDebug LED, if it's the BIOS, the CPU itself or anything else.

Does anyone know what I should do next?

 

[Vikeo]

I tested the CPU on another motherboard (MSI B450 Tomahawk MAX) and it works fine on it, as do the other component.

I think that flashing the bios wrongly is the problem. When I did it I thought "surely you can't flash a bios that doesn't work on here", but maybe you can.. Well, leason learned.

 

[Vikeo]

I've managed to flash the correct bios onto the B450M Mortar Max motherboard. I used a different USB stick than I first used, and that just worked. Didn't see any guide recommening using a different USB stick if flashback doesn't work. First I used a 2.0 stick that didn't work, then a 3.0 stick that did work, if that matters.

Hopefully this helps some others in the future.

 

[Vikeo]

The computer stopped booting once again yesterday, but now it's hopefully fine. There was a little bit of thermal paste next to the CPU socket. Don't know if it was there when I got it (it was used) or if I did it myself, but when I removed it it started booting again. I had seen it before today but it didn't look out of place so I didn't think it was anything harmful.

Hopefully it keeps working.

TLDR: Don't flash the wrong bios. Check motherboard for any thermal paste.