Question Computer randomly switched off and now it won't start up ?

Aug 28, 2022
Hey, Im wondering if someone can help me.

Ive had my computer for a number of years and randomly 2 days ago while playing a game the computer completely switched off. The RGB on my RAM will light up but nothing else works, no fan spin up or anything.

Current set up is:

Gigabyte AORUS B550 Elite.
AMD Ryzen 3600
Nvidia 2070
Corsair Vengeance RGB RAM
Corsair 750W PSU
Sahara P35 Case.

I have tried a new Gigabyte B550 Elite V2 and that results in the same thing, no power, no fan spin up, only the RGB RAM lights up.
I have tried powering the MB using the PSU from another PC, same thing.

I have tried the RAM in my partners almost identical PC, that works.
I have put my CPU in the other PC, that works
I have moved the GPU to the other PC, that works.

Im worried there is something wrong with the PSU or case (unsure if a case can cause this) and that by putting the new MB on the old potentially faulty PSU it has caused the same problem with the new board ?

Any suggestions of what to do/ what it could be?