Mmmh... I never heard of this before. If you press F1 does it bring up the option menu for RPG Maker (If so, you can check the keyboard settings)? Do you have other RPG Maker VX Ace games you could try to see if the problem extends to other games from the same engine? Do you have some "unusual" input devices plugged in (like, tablets, off-brand controllers, etc.)? Which version of windows are you on?
You might also want to check this thread: https://forums.rpgmakerweb.com/index.php?threads/normal-keyboard-inputs-not-work...