You’re probably complicating something more than you need to. This should be a very simple thing to build!
Are you trying to make references to these chests in some other blueprint? Level blueprint, or something? If so, those references might be confused.
Try just building a single chest, with a reward, and an opening effect/animation. And a bool for whether it’s already opened.
Then, add an overlap detection test, and make it detect pawns. When begin overlap, check if not yet opened, then cast to player pawn, if it works, play the animation and give the reward to the player and set the “opened” flag.
You should be able to drag many of these into the world, and they should each work when you walk into the area.
You should also be able to “create child blueprint” class, and re-configure that child with different effects/rewards, and place instances of that, too.
Now, once that works, you might want to change the overlap actor to instead register itself as an “interactable” for the player, and have the player display “press E to Do The Thing” when it has an interactable. Also, un-register the chest as interactable when overlap ends. Or whatever interaction mechanism you actually prefer, rather than just “bump into chest.”