Raptorkillz As I said the built in actions may be "overriding" your defined actions if both are mapped to same input events. What gets printed as "current sequence" when you press left/righ/up/down actions?
You can try with this input function instead. It prioritizes last added actions:
func _input(e):
var actions = InputMap.get_actions().filter(func(aa): return e.is_action_pressed(aa))
if actions:
var a = actions[-1]
s += a if not s else " " + a
print("current sequence: ", s)
for k in cheats.keys(): if s.contains(k): cheat_code_entered.emit(cheats[k]); s = ""