Press FN + F6

On Alienware laptops, the F6 key has no visible sub-function.  But, you have probably accidentally pressed it while intended to increase the volume with FN + F5.  This has shut off the Windows Key… without any indication or warning.

The fix for your Alienware Windows Key is:

Press FN + F6

FN + F6 toggles (enables / disables) your Windows key.