I have a gray screen. I can access computer on an alternate monitor, would like to fix screen.

[Krowsman]

I have a gray screen. I can access computer on an alternate monitor, would like to fix screen. I've checked video driver and hard restart.

[BeemerBiker]

Did this problem happen after a power surge?  After a BIOS update?  After a Microsoft update?

I looked up your model ID and found several drivers available

https://support.hp.com/us-en/drivers/selfservice/hp-pavilion-23-q200-all-in-one-desktop-pc-series-to...

There is something suspicious. Drivers are supplied for both "Intel HD" and "Discrete AMD" graphics.

The motherboard is identified as a Crane-U and supposedly has the Intel H110 chipset.  There is no mention of AMD graphics

Something is wrong and that may have caused the gray screen. 

I am going to assume you have an Intel CPU and the CPU has built-in "HD" graphics and there was no power surge or hardware defect.

Please bring up the device manager and look for any error alert icons.  They will be yellow or red and might be hard to see

for example

 I am guessing that the wrong driver was installed.

Try to roll back the driver or simply uninstall it

Do that for all devices that had the yellow alert.

Then select "scan for new hardware"  with a right mouse click

if the above does now work (you may need to reboot) then

Please use the windows key plus "shift" plus "S" to copy and paste the problem device here so it can be interpreted.

There may be more than one alert.

Another option is to retore windows 10 to the last time the monitor was working correclty.

click this link then scroll down and expand "Restore from a system restore point"

This assumes there are restore points from when the display was last working.

There have been no bios updates since 2019.   You might check the release date of the BIOS and see if you have the latest for your Board ID.