Question RTX 3090 Suprim x No Signal

[Taqu]

Hello, i bought an new rtx 3090 suprim x of an guy that said it was new. I saw alot of threads where people are having the same issue as i have and getting no signal. Although when i insert my gtx 970 into my mainboard it works perfectly fine. every port doesnt work btw, hdmi or dp its absolutely not my monitor thats causing this issue. When i insert the hdmi cable into the graphics card, it says searching for signal on the monitor, so its knowing an cable got plugged in. I tried pretty much everything:

-updatet bios to latest
-made ddu before installing
-updated nvidia drivers
-tried that thing with the single ram stick

System
Mainboard: Asus Rog crosshair viii dark hero
PSU: Corsair rm850x
cpu: ryzen 5 5600x

If you have any other questions or might have an suggestion what this might cause please write an comment im really open for any suggestion and try anything, i just want to get this to work.

 

[zx128k]

Are all the 8-pin connectors connected on the graphics card? Do the lights and fans spin of the graphics card?

 

[Taqu]

Are all the 8-pin connectors connected on the graphics card? Do the lights and fans spin of the graphics card?

Yes, it lights up all fans are spinning. All are connected no daisy chaining

 

[norcalsc]

have you tried different cables?

 

[joan16v]

Try on another PC...

 

[Taqu]

i mean the cables are working on the gtx 970 too so i think its not by the cables. And theres noone that has an pc i know. And it should work because the gtx 970 works perfectly on there.