Question PC won't post after plugging new GPU

[Scallos]

Hello!
I recently bought an msi 3090 suprim to upgrade my 3070, but now it won't post.
My computer has:
b450 tomahawk max
ryzen 5800x3d
evga supernova g3 750w
32gb oloy ram 3200mhz

Everything was working fine before switching the gpus.
After switching it, I wouldn't get display signal and the mobos CPU red light would come on.
I was worried the card may be faulty, so I tried the 3070 again, but no luck. Same error. Can't even use the PC now.
Then I tried another PSU i had, a Redragon 500W one, with the 3070 (since it doesn't have enough power outputs for the 3090) and it worked.
Then I tried using the redragon PSU to power the cpu+mobo and the EVGA psu to power the 3070. It worked
Then i tried the same config but with the 3090 and it didn't work.

Today, a friend of mine brought their Corsair Hx1000 psu
We just tried powering thr entire system with it, but it doesn't work


I'm at a loss, don't know what could be the problem or why the 500W psu works but the others don't

Any suggestions are appreciated

 

[helpstar]

update the BIOS of the motherboard

eventually loose contact of cable/pin of PSU

 

[Scallos]

updated the BIOS... no luck. What's also weird is that the pc doesn't quite shut down now, fans just start spinning faster and lights are stull on. i also get the cpu red light.
when i tried flashing it, it did this as well so i had to manually shut it down from the psu.

maybe its the cpu? weird....

 

[NeedHelpYikes]

I'm in a similar position, did you ever get this figured out / fixed?