Question is, where are you calling the Left Mouse Button event from? From the Player Pawn? From the Player Controller?
If you are calling it from the AI actor then it’s just normal that it doesn’t fire.
You should follow franktech’s suggestions, move your logic to a custom event in the AI blueprint, then from your player controller/pawn catch the left mouse button event, on fire find your actor using “Get all actors of class” or in any other way, and call the custom event