Question PC won't turn on. What could be the problem with my PSU?

[Tottem]

Setup
CPU: AMD Ryzen 5 5500
RAM: Kingston Fury 3200MHz DDR4 8GB x2
Motherboard: Gigabyte B450M DS3H
GPU: NVIDIA GTX 950 [7.5 years old]
SSD: Kingston A400 240GB [5+ years old]
HDD: WD 1TB 7200RPM [5+ years old]
NEW PSU: Cooler Master MWE 550W 80+ Gold FM (Used, from a friend, he said he only used it for like 6-9 months, it was purchased about 2.5years ago, changed because 550W wasn't enough for his new GPU)
OLD PSU: Cooler Master Elite Power 600W (RS-600-ACAB-M4) [7.5 years old]
OS: Windows 10
*BIOS version: F63
*Using an extension cord
*Tried turning it on while plugged into a direct wall outlet, didn't work

I bought new CPU, RAM and Motherboard in the middle of december. I set it up, everything works fine until after 1.5 weeks, when my PC starts shutting down randomly few minutes into running League / CSGO. It doesn't overheat(shuts down at around 60°C). I did a stress test with AIDA64, and it crashes after 3-4 minutes. Event viewer says Error 41. I decided to take my OLD PSU out, and my friend gave me his barely used PSU.

1st day: I set up my PC with his PSU, do a stress test, try games, everything works fine.
2nd day: I try to turn PC on, nothing happens. I remove NEW PSU, plug in my OLD PSU, try turning it on, it works, I turn it off after a minute, remove OLD PSU, plug in NEW PSU, PC turns on, everything seems normal
3rd day: I tried the same thing as on 2nd day, but it didn't turn on. The fans won't move, no light from mobo, nor from peripherials, no BIOS.

I left the PC turned off for about 8 days, with the PSU also turned off, and this process repeated itself
1st day (09.01.): Runs fine
2nd day (10.01.): Issues with starting up

Other info:
I reinserted one RAM, replugged the HDD, SSD cables, slightly moved the PCIe cable (on the GPU end), and it turned on
Issue seems to come out overnight
If I let it be with PSU turned off for a few hours, it can be turned on

Edit: *

 

[Lutfij]

Welcome to the forums, newcomer!

OLD PSU: Cooler Master Elite Power 600W (RS-600-ACAB-M4) [7.5 years old]
NEW PSU: Cooler Master MWE 550W 80+ Gold FM
The Elite unit you previously had is a bad unit. Should be dealt with as if you were dealing with a paperweight. Not kidding, that unit does not belong anywhere near a PC.

I bought new CPU, RAM and Motherboard in the middle of december.
Did you perform an OS reinstall after you migrated to the new motherboard? If you're able to get into BIOS, now would be a good time to check and see what your current BIOS version for your motherboard is.

I left the PC turned off for about 8 days, with the PSU also turned off, and this process repeated itself
1st day (09.01.): Runs fine
2nd day (10.01.): Issues with starting up
Seems to me that you're having a grounding issue if replacing parts is what causes the system to revive. Can you relocate to another wall outlet in youe abode?

 

[Vic 40]

Powered directly from the wall? Or using a extension cable of some sort ....

 

[Tottem]

Thanks for the answer Lutfij!

"Did you perform an OS reinstall after you migrated to the new motherboard? If you're able to get into BIOS, now would be a good time to check and see what your current BIOS version for your motherboard is. "

I did a OS reinstall. BIOS version is F63.

"Seems to me that you're having a grounding issue if replacing parts is what causes the system to revive "
"The other way to revive it is by turning the power supply off/unplugging it from extension cord ".

So if I leave the PSU switch on, it won't turn on the next day, unless I unplug the PSU and wait a specific amount of time (not sure how much that is, it worked after 4 hours yesterday)

"Can you relocate to another wall outlet in youe abode ? "

As of now, the PC turned on as the PSU was removed for 6 hours, but after a few hours in, I will try another wall outlet. The PSU needs to be used for a short while before it shows this issue after turning it off. Is there anything I can do in the meantime?

 

[Tottem]

Powered directly from the wall? Or using a extension cable of some sort ....

I'm using an extension cable as the room is set up in a way where my PC power cable can't reach wall outlets from the table, but I can move the pc itself for testing without the monitor if needed.

 

[Vic 40]

Test without the extension, see how it behaves.

 

[Tottem]

I plugged the PC into a wall outlet, didn't work. I also tried outlets in other areas of the house, and those didn't work either.