I THINK I see the problem. Let me hazard a guess: you can fire again right away, but you CAN’T actually build up a charge again, right?
Try this: make firing the projectile hit a sequence node. First, it will close the gate after “Release” (same as right-click), THEN it will hit the delay that eventually reopens the first gate.
Right now your delay prevents you from charging until the cooldown is over, but your release command will still fire, so you can fire uncharged shots. If you gate that shut, you won’t be able to do either… Though once the cooldown is over and you can initiate the charge again, it will hit the sequence that re-opens the release key.
I caution you, though: you may find this setup frustrates the player. If they hold charge before that cooldown window is open, it won’t register… And even after the cooldown is over, it still won’t register, as you won’t have generated a NEW “Pressed” event. IMO the intuitive way is for holding the button to “prime” a charge, so that once the cooldown is over, it will start charging right away if you pressed the key before the cooldown was finished.