I don’t have access to UE as I write this, but here are a few things you can try:
Try printing a string after OnActorBeginOverlap to see, if the overlap is actually triggered. If it is, try dragging off of Other Actor and casting to your characters class (in this case FirstPersonCharacter). Then ‘As FirstPersonCharacter’ should give you the option to call your event.
I’m assuming this is not a multiplayer game, if nothing of this works, I don’t know whats wrong 