We had successfully been running a touchscreen experiment with no issues for a couple of months.
We didn't change anything on the system ourselves.
The system is a Dell Inspiron laptop with AMD CPU and integrated Radeon graphics, and a separate touchscreen is connected via usb and hdmi.
I recalled a while ago installing the AMD Adrenaline software, and the touchscreen will then fail to show any graphics during the monkeylogic task (but works fine otherwise)
After uninstalling all AMD software, (but keeping Microsoft C++ installed), it worked fine.
However, we found yesterday the system just stopped running the experiment, touches on the screen still worked, but no stimuli appeared, just a black screen, but when the task is turned off, the touchscreen functions as normal.
There's nothing wrong with the touchscreen, because we had an identical laptop (we bought backups, since monkeys are rough and accidents happen), and the identical laptop plugged in just fine, and everything in the task worked.
Unfortunately, try as I might on the original system, I simply could not get it working again. I uninstalled and reinstalled monkeylogic, the visual C++ software (took it directly from the NIMH website link), MATLAB 2023a, tried again on 2023b, reinstalled uninstalled all AMD drivers, in the end I literally clean installed windows 10 again, and still, its the same problem, screen works fine in all cases except when the task begins, at which point it goes black and nothing appears.
I have since made a full system backup of the working system, now that I know this can happen, but since there wasn't a restore point setup on the original system, I don't have a way to go back. I could probably clone all the settings/drivers from the working system onto the old system, since the hardware is identical, but that's quite a hassle.
Do you happen to have any advice on this, before I do that? Thanks!

Have you tried changing the background color, let's say, to red? Does the touchscreen still go black, instead of red?

Try the instructions in the following link. You may need to change the coordinates in "Fallback screen rect." ([left, top, right, bottom]) to make the fallback screen show up on the touchscreen side. Click the "Test" button in the figure. What happens? Does checking on "Forced use of fallback screen" make any difference?
https://monkeylogic.nimh.nih.gov/docs_MonitorSetup.html#SingleMonitor

The background color of my screen had always been set to a different color, gray, but it doesn't show up that way, its black.
Just now, my "working system" has stopped working as well.
I had checked, my system had an AMD Ryzen 5825, and it had integrated Radeon graphics.
The working system had GPU drivers from 3/30/2023, and had been fine.
Once used for a bit, I'm guessing it started auto updating (luckily I had grabbed a snapshot before then), and it changed it to the 7/31/2023, after which it ran into the same problem.
One of the things I had tried was updating to the latest GPU drivers as of yesterday, but those didn't work either.
It's currently running in "extend these monitors" mode, and there's two.
Tomorrow I'll test out your suggestions, but it does appear something in the latest AMD update is breaking how monkeylogic is handling graphics.

I highly doubt that it is a driver problem, but I guess it is not impossible.

Thanks for this, your suggestion of treating it as a fallback screen was able to resolve the issue.
In case anyone runs into a similar problem, here's precisely how I solved it.
My system consisted of a laptop screen, which will be Screen #1.
Connected via USB+HDMI was an HMTECH 10" touchscreen for raspberry pi, which I picked for its low cost, its compatible with standard windows 10, and since it has no case, I could spread some consumer grade "liquid glass hardener" for strength (across all of our use, although after a few months this screen type has had its touchscreen ability fail (probably digitizer) after many monkey punches, the screen has not yet cracked), and as one more safety layer, we put one more layer of standard plastic screen protector on the surface, so even if it was to crack, glass would be contained until the unit could be swapped for a fresh screen with similar modifications in our customized case that is home cage mountable. This is Screen #2.

When I first purchased the laptop, I chose one that was mid range, that contained AMD graphics, since I had noticed that photodiode tuning required AMD graphics (we do not plan to use photodiode with this system, I just figured AMD might result in fewer driver incompatibilities, an assumption that might not be correct now, as a different lower grade intel system with integrated graphics has been running with no issue since we've created our setup). Previously our AMD laptop had worked "plug and play", screen #2 was selected as the subject screen, and no additional configuration was necessary.
After investigation it appears that a "normal windows update", had updated the AMD graphics driver, and now this "plug and play functionality" has ended. Changing the background color to a different color still shows it as black, although in "extend display mode", all normal functionality on the screen #2 was fine, it was just when the task was started that it shows as blank.

In windows Duplicate and extend settings menu, after setting the screens to

1 | 2

I selected Screen #1 as the subject screen (does not work if screen #2 is selected, even if the other orientation is correct), and set the fallback coordinates to [1920,0,3840,1080] after which point, with "forced use of fallback screen checked", it does now work again.
It is strange, because the operating system definitely recognizes Screen #2 as a separate screen (with resolution 1920x1080), and during normal windows operation, such as moving windows around, dragging programs from one screen to another, all that works just fine, its just when the "low level monkeylogic stimuli appear", and if they are generated on screen #2, it shows an entirely black screen, no matter what the background color is set to. Though, when generated on screen #1, it works.