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.