How to create a functional variable of a character using a parent from a c++ plugin?

Hello I use a plugin called Multiplayer Shooter Plugin which adds BP and C++ code to facilitate the creation of a multiplayer shooter. I therefore use a character having a character in C++ as a parent I want to create a boolean variable in order to set up an aiming animation for this I have created a variable from the child in BP but when I press the key that changes the value of the boolean does not work as if the variable did not work in the child (I did create the transitions between idle and aiming so it does not come from that) do you have any idea?