I built a watercooled PC, and as part of it I wanted a 5 inch monitor to show the current temps of my system. I am using Win11 (which is fully updated), a Gigabyte 3090 Waterforce (which is using the latest driver - 528.02) which is connected to MOBO via LianLi 34.0 PCIe riser cable,  and an ASUS z690 Hero  MOBO (with as updated drivers as I can get). My problem is that when I plug in the monitor, Win11 recognizes it, but it only displays a grey screen. The really weird part is that when I previously switched to a different HDMI output on the 3090 to the monitor, the display worked, momentarily, then reverted back to a grey screen. I reformatted my drive, and since I do not have any software on here except for drivers, I am at a loss as to how to get my external monitor to work.
 
Neither of my two 4k monitors, connected via DP, have an issue.
 
Thoughts? 
 
And thank you in advance.
 
Edit to add PCIe riser cable info...

Scourge78
I built a watercooled PC, and as part of it I wanted a 5 inch monitor to show the current temps of my system. I am using Win11 (which is fully updated), a Gigabyte 3090 Waterforce (which is using the latest driver - 528.02) and an ASUS z690 Hero  MOBO (with as updated drivers as I can get). My problem is that when I plug in the monitor, Win11 recognizes it, but it only displays a grey screen. The really weird part is that when I previously switched to a different HDMI output on the 3090 to the monitor, the display worked, momentarily, then reverted back to a grey screen. I reformatted my drive, and since I do not have any software on here except for drivers, I am at a loss as to how to get my external monitor to work.
 
Neither of my two 4k monitors, connected via DP, have an issue.
 
Thoughts? 
 
And thank you in advance.

With two 4K monitors connected a third is going exceed the maximum output resolution of the GPU of 7680x4320 at 60hz.

I suppose that is a possibility, but when I completely unplugged one 4k monitor and plugged in the small one, the same thing happens- grey screen.
 
Could I change the resolution on the big one down, and thus enable all three? And if it isn't the resolution limit, any other ideas?

Two 4k monitors does not exceed the resolution limit. 7680x4320 means the card can push 33,177,600 pixels aka four 4k monitors. The specs of the 3090 even states it can support four displays. Something is going on with your display, display cable, or gpu output since the display worked momentarily.

Does anyone think that a PCIe riser cable would be the problem? Because my VGA is using a PCIe 4.0 riser cable.
 
I apologize if that is important and I didn't mention it to start with.

Scourge78
Does anyone think that a PCIe riser cable would be the problem? Because my VGA is using a PCIe 4.0 riser cable.
 
I apologize if that is important and I didn't mention it to start with.

 
If you can run two monitors @ 4K  .... not very likely a PCIe riser issue
 
What settings are you using in Nvidia Control panel?
 
Any Device Manager errors?
 
Where are you getting the temp data from ?
 
List all other software running ... from Asus or any AIO cooler
 
excerpt from first Post "I wanted a 5 inch monitor to show the current temps of my system"
 
Need some more Details on that 5" screen:  

Mfg & part number


Resolution & Color saturation supported
 
Ports available on this monitor
 
Monitor driver 

Any Mfg recommendations, for specific software, to support this as a secondary use monitor (not a desktop duplication or extension)
 
Can you see this 5 in monitor in Nvidia software?  What settings are you using

All Nvidia CP values are the defaults, so I am not sure what to report. It says that the display is connected via DVI, but it is really connected via HDMI (not sure how to change that). Win11 and NvidiaCP show the monitor (native res 800*480) as recognized, but it won't display any thing other than grey. Device MGR also recognizes it as a generic display (with no further info). There are no errors for the displays ( I'm trying to geta a USB hub to work, which is showing a bunch of errors, but it is currently unpowered and unplugged). Display res is 800*480
 
Software- drivers for VGA, Rainmeter and 2 skins, VLC media player, Steam games, ASUS Armory Crate, RGB control for Corsair and Gigabyte, HWInfo. However, this issue continued even after a clean reformat and the sole loading of Nvidia GPU driver 528.02, before any other software was loaded. I loaded AIDA64 as recommended, but even after getting it configured, the screen still shows as grey. Temp values are also fed via HWInfo.
 
https://www.performance-pcs.com/peripherals/lcd-displays/lcd-video-modules/ppcs-mini-monitor-mod-5-inch-ppcs-mini-monitor-5in.html
 
Specifications:
Case dimensions: Approx. 146mm x 95mm x 17mm (LxWxD)
Dimensions w/stand installed: Approx. 146mm x 95mm x 98mm (LxWxD)
Display dimensions: 110mm x 66mm (LxW)
Ports: HDMI
Screen Type: TFT LCD
Screen Resolution: 800x480
Case material: Acrylic
 
 

I would wonder if the monitor might be having a copy protection problem. It might be worth trying a different cable. The copy protection check can trigger the grey screen even if no copy protected content is displayed.

Hoggle
I would wonder if the monitor might be having a copy protection problem. It might be worth trying a different cable. The copy protection check can trigger the grey screen even if no copy protected content is displayed.

Nope, just tried two different cables. No luck.

W11 there are settings in Windows you should/must use
 
When you say it is "GRAY" - do you mean the "image in settings"?
 
try ---> Windows logo Key + Ctrl + Shift + B
 
 
Have you tried all the steps listed in these?
 
How to set up multiple monitors on Windows 11
 
How to use multiple monitors in Windows
 
How to fix external display not working on Windows 11