Since you have an add-in video card, make sure the monitor is correctly connected to the card, not to Intel Graphics. What video port are you using on video card and on monitor? Is the video card a Dell OEM card or did you install a "retail" card?  Can you test this monitor on a different PC or different monitor on this PC, just to rule it out? You could try clearing BIOS: If that doesn't help, physically remove the add-in video card and try using an onboard Intel Graphics port. BTW: Are all your personal files backed up on external media?
My Dell XPS 8930, which is running Windows 11, will no longer start. I performed a routine Windows update, but now when I go to start the computer, nothing appears on my monitor. The computer turns on, the fans operate, the caps and numbers lock keys light up, and there is a steady green LED glowing on the back of the computer. But nothing appears on the screen ... no Dell logo, nothing. I think I can hear the hard drives active in the comuter, and the DVD drive seems to work. I put a Windows ISO disk in it, but nothing appeared on the screen. I removed and re-seated the RAM and the video card, and confirmed that the CMOS battery has plenty of power. There's nothing wrong with my monitor because I plugged another computer into it and it works fine. Anybody have any ideas? Thanks.
XPS 8930, won't start after Windows 11 update