Can't get the new Input System to work with the Kart Microgame

I'm making a ve$$anonymous$$cle based game so i'm using the Kart Microgame as a base, since the Microgame uses the old Input System i'm trying to update it to use the new Input System, however, i cannot add the Input System namespace `using UnityEngine.InputSystem`. I know that the package is correctly installed because i can use it in any other script outside of the Microgame ones, any ideas?