My 3090 FTW3 switches off output when I start more demanding games like cyberpunk or starfield. Black screen and monitor says no input. Usually as soon as the game play starts. Low power use browsing or video is working fine. Before I RMA I would like to trouble shoot though.

What PSU are you using? Sounds like insufficient power from PSU

Part Number: 220-G5-1000-X1
Part Desc: EVGA SuperNOVA 1000 G5, 80 Plus Gold 1000W
 
Was working fine for the past two years. I can hook up a 1600W power supply and see if that is the issue.

Emparus
Part Number: 220-G5-1000-X1
Part Desc: EVGA SuperNOVA 1000 G5, 80 Plus Gold 1000W

Was working fine for the past two year. I can hook up a 1600W power supply and see if that is the issue.

Good idea, I've had those type issues b/4. Heck Corsair sent me three different psu,s while I was hammering on 3DMARK kept burning them puppies out. 1200w Finally sent me a 1050w and the problem when away. The 1200w ones were actually two 500,s wired together. I7 965EE EVGA Gtx 580 sli it's in my profile pic.
Still have the case like new in it's original box they stamped the serial number on those sense there were like 500 world wide

Good call. Definitely a power supply issue. Looks like the EVGA G5 is going down. Still on warranty though. Probably getting an updated one with more power though.