Ok first of all, what is the Actor Reference in the Wool actor? Is that a reference of the HUD? Where do you set that? If it is the HUD, you can just get "PlayerController 0" and "GetHUD" and then cast it to your HUD Class to increment the int variable that is in the HUD Class.
Summary: Delete "ActorReference" variable in HUD Blueprint. Remove the whole "GetAllActorsOfClass" part.
Delete the "Number_Of_Coin" variable in your WOOL Blueprint, you don't need that. It is already in the HUD. Also remove the "ActorReference" variable there too.
Get the PlayerController0. Get the HUD from it. Cast the HUD to your custom HUD BP. Get the Int variable from it and increment that.
Extra Information: Use an "IsValid" node for your Reference variable to make sure that they are not NULL (they can be empty if you don't full them).
Avoid using "GetAllActorsOfClass". This is an expensive node. Try to get the reference otherwise. For example by either Spawning the Actor and saving it directly in a variable.
OR (if the actor is already spawned) select it and create a directly reference in the LevelBlueprint
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