Explorer has some bug evidently which stop listening for the shortcut key. The Windows key still works, but the key sequence Windows + Arrow is ignored by the OS.
solution :
restart explorer.exe
1way End the process tree, by task manager
2way use powershell :
1
kill -name explorer
src - https://superuser.com/a/1137568
origin - http://www.pipiscrew.com/?p=9975 win-key-arrow-does-not-snap-windows-on-win10