Sorry needed to edit my reply since I see you have a Laptop with a mobile AMD APU processor and Nvidia GPU card.
Go to Device Manager and make sure under "Display" there are no errors and both the Nvidia and AMD GPU are enabled.
Possibly in you installed AMD basic Mobile Graphic driver there might be some conflict with the Nvidia GPU driver.
I would first install your laptop's Support AMD OEM Graphics driver and see if DXDIAG now shows up.
Download GPU-Z and upload an image for your AMD IGPU. This will show you if the AMD driver is correctly installed and functioning the way it should.
At the bottom of GPU-Z you can select either Nivida or AMD GPU to show.
IF everything works fine with your laptop's AMD OEM Graphics driver installed and it is very out-dated than you can download AMD's basic Mobile Graphics driver and see how that works:
Latest Mobile AMD GPU driver for the 4800H: https://www.amd.com/en/support/downloads/drivers.html/processors/ryzen/ryzen-4000-series/amd-ryzen-7...
Previous AMD GPU Driver for the 4800H: https://www.amd.com/en/support/downloads/previous-drivers.html/processors/ryzen/ryzen-4000-series/am...
The previous AMD GPU drivers in case the latest AMD driver is not working the way it should.