If you suddenly cannot type A, W, S, D on your keyboard, maybe these keys were actually remapped to arrow keys. This could happen during playing a game. Most keyboard can fix this if you press [Fn] key and then [w] key holding both pressed. This should switch the mapping of the keys back to letters and arrows. More in this video here:
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Windows key not working This can also happen. And I managed to sort it by pressing [Fn] key and then [Windows] key.