Variant: Ctrl-N Ctrl+N stopped working
I came across an equivalent problem today but "Windows Key" was not affected which made it harder to find a solution. Only Ctrl-N didn't work and it looked like a text editor glitch, but then it didn't work in browsers and the only "solution" visible on the net was ridiculous (reinstall driver - yeah right :-).
On-Screen keyboard (Win+R OSK Enter) served as a diagnostic tool, showing that Ctrl-N was really not getting propagated but that a browser (or editor) does receive Ctrl-N from OSK.
The Ctrl+Alt+Del and then Esc (to simply go back - the whole point is not to interrupt your running stuff).
It took some time for the logoff/lock/switch screen to show op => Windoze does perform a light UI-related reset on Ctrl-Alt-Del and something was stuck or slightly messed up.
The only suspicious thing within the past few days was that I've found a MaskVPN process and eradicated the whole thing manually (MaskVPN is nominally legit but is used by some malware as "self protection", Win Defender never screamed a fault so it was probably from some game on AppStore - they only things I installed for the past week+).
MaskVPN has a deamon that's visible in ProcExp but you can't spot it unless you are checking. I have a habit of checking processes in perpetually running ProcExp once in a week or two and MaskVPN has been eradicated a few days before I noticed the Ctrl-N problem (not using it frequently).