Add Item into Character's Array From Box Trigger

I’m working on my first RPG in Unreal and I’m having trouble setting up the inventory system. My initial thoughts were to store all the stats and items inside the ThirdPersonCharacter blueprint because I wanted them to carry over from level to level without having to copy it over everytime.

So, I have an array called “Inventory” which will hold all the items (potions, weapons, armor, etc) in the ThirdPersonCharacter blueprint and a box trigger that holds an item I want to add to the character’s inventory. Upon overlap and when the player hits the return key, I call a funtion “AddToInventory” inside the character’s blueprint which should take the item from the trigger box and add it to the Inventory array. Think of it like walking up to a treasure chest, hitting a button and collecting an item. However, I keep getting the same error and I don’t know why. I’ve been struggling with this for the past week and nothing I’ve tried works. All the tutorials I’ve looked at were very basic movement operations on an actor and didn’t really help in my case. If anyone has any experience or knowledge on this, I would greatly appreciate the help!