Another idea
Have you ever used a second and larger screen?
Your computer may think it is still there. If the second screen is set to duplicate then the image on smaller first screen is shifted left right up and down when you move your cursor towards the edges. And you are close to the edge on the taskbar. Hence the window you just opened may be shifted off the screen on the moment the cursor left the taskbar.
So please check you display settings, even if you did not use a second screen, whether you are using the correct pixel size for your screen