Strange indeed.
See if anything in https://www.google.com/search?q=file+explorer+window+doesn%27t+show helps you.
If not, things to try:
1. System restore back to when it still worked OK.
2. sfc /scannow from the command prompt (in elevated mode)
3. Back to your latest image backup.
4. Refresh Windows (keeping all programs)
5. Reset Windows (but then you've got to reinstall all).
The Windows file explorer window in my PC doesn't show and pop up anymore in my Windows 10 computer. It does highlight on the Windows taskbar where I can see that that window is opened and also, I can hover over it with my mouse cursor and then its little explorer window icon pops up on the task bar but that's it, the big window itself doesn't show up or is accessible anywhere.
I have all latest updates of Windows 10 installed. What I tried already: I uninstalled a couple of apps which I think I had installed around the time this problem started happening. And I also updated all my drivers with my paid/premium driver update software. But all with no success.
I never had this kind of problem before and I don't know what else to do.
I could uninstall all remaining apps on my PC one by one and see if that fixes it but those are still quite a lot of apps and then I would need to re-install them later again. Not sure if I should do that.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic