First download the latest driver Geforce Driver Results | NVIDIA
After restarting the computer, right click the desktop and go into the nVidia Control Panel. Setup Multiple Monitors. Go to the Toolbar to Display/Identify displays. Does it show all 3 monitors?
If not, Press the Windows key+X and choose Device Manager, Expand Monitors, all all 3 monitors showing there?
If not, While the computer is on start switching the cables to the working monitors to the one that is not. Keeping switching the order around plugging them in in different order.
If all 3 monitors are showing in the areas above but there is no signal, then the Resolution might be set too high for the 3rd monitor.

 

First download the latest driver Geforce Driver Results | NVIDIA
After restarting the computer, right click the desktop and go into the nVidia Control Panel. Setup Multiple Monitors. Go to the Toolbar to Display/Identify displays. Does it show all 3 monitors?
If not, Press the Windows key+X and choose Device Manager, Expand Monitors, all all 3 monitors showing there?
If not, While the computer is on start switching the cables to the working monitors to the one that is not. Keeping switching the order around plugging them in in different order.
If all 3 monitors are showing in the areas above but there is no signal, then the Resolution might be set too high for the 3rd monitor.

Thanks!
So i have it booting with all three monitors working... however there is a new issue.
In order to have all three monitors on, i have to unplug one of my monitors, boot to windows, then plug the monitor back in. then all three work fine until i power off the system.
if i boot the device with all three monitors plugged in, i get my Mobo Boot screen, then blanks out and no signal from all 3 monitors.

Any insight? Thanks again so much for your help

 

Your video card may need a firmware update. This may or may not apply to your situaiton, you decide.

Nvidia has released a firmware update tool for its new GeForce RTX 4090 and 4080 GPUs to fix a bug that could break display output, causing the GPU to show a blank screen when being used without drivers installed. The issue only affects "certain motherboards," and Nvidia says it "should only be applied if blank screens are occurring on boot."

Nvidia releases RTX 4090 and 4080 firmware update to fix display output bug

Update can be installed on both Founders Edition and third-party GeForce GPUs.

arstechnica.com

 

Your video card may need a firmware update. This may or may not apply to your situaiton, you decide.

Nvidia releases RTX 4090 and 4080 firmware update to fix display output bug

Update can be installed on both Founders Edition and third-party GeForce GPUs.

arstechnica.com

 

One person with the same problem you are having reset all of his monitors to factory settings and it solved the issue. How to do this will vary depending on the make and model of the monitors.

 

so, this "fixes" the issue, but for some reason, when i switch my monitor to 240hz, my displays black out.
normally i would say its an overload, but when i start the PC with 2 plugged in, and plug in the third after its booted, i can use my monitor at 240 hz without issue. (also im using a 4090, it shouldn't be overpowered at 240hz

so essentially, currently, if i want to game at 240hz, i have to unplug a monitor before booting every time.