Nereus
Try plugging your DP cable in another port from your 3090 card. Also you might need to buy a certified DP1.4 cable, seems a few people have found a sub-standard DP cable to be the issue (or HDMI if you're using that).
Tried that and it didn't work. Now, the GPU has a red LED and no RGB - it seems completely dead. This is really infuriating. I swapped my RTX 3090 FE into the system with the same cables/monitors etc. and it works flawlessly. Just live streamed for over 1.5 hours with no issues at all - and I had the GPU OC'd as well. A side note, the FE card was ~ 10C cooler than the FTW3 Ultra with the same setup - that is quite surprising.
Anyway, I'm not sure if I have to RMA the card now or if there's a way to recover it - there's just a red LED when the PC starts and no video signal in any of the ports - tried 3 different ports (DP 1.4) and a HDMI connection - on 3 different monitors - zero video signal from the FTW3 Ultra.
My DP 1.4 cables are certified for 4K 120Hz.