Does your Overlap actually fire? Put a print string between it and the Player Touches Ball function.
If it does, then just drag off the Other Actor pin, cast to whatever your character blueprint is called, and call the Player Touches Ball from there.
So I made a custom event on a blueprint but when it should fire, the game ignores it totally.
(btw. I created the custom event on my character and I try to call it on the ball blueprint)
Yes that casting worked, thanks!