Nice question. Solved the problem for me. I have a Corsair K70 RGB, with this Windows button lock button. It was turned on, to prevent Start menu breaks when in-game. Never used it, so I didn't think of it until you asked that question.
Thanks!
Added comment, as this was an early hit on google on this issue.
An old post, but I had the problem recently and the problem may be of interest to others.
In my situation, WIN+D (Show Desktop) stops working whenever I start debugging with Microsoft Visual Studio 2019 Professional (I did not notice this issue when using the Community version of VS 2019). As soon as you start debugging, WIN+D stops working regardless of whether VS2019 (or the application being debugged) is in the foreground or background. Stop debugging...and WIN+D starts working again. No other WIN+?? keys are affected, as far as I can tell, only WIN+D.
Unfortuantely, I do not know how to stop VS2019 interfering with WIN+D (apart from not debugging!) and I do not know whether other versions of Visual Studio are affected.
Thanks to @dalchina's comment which prompted me to close running programs and work out the culprit.
Sorry to bump this old thread but I was having this problem on an HP EliteBook Folio 9470m and it resolved itself a few seconds after I turned tablet mode ON for a few seconds and then OFF again.
Could be a coincidence but might be worth a try.
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