Hi,
The reason your interface is not working is that you’re trying to call the function as if your FirstPersonCharacter implements it. Your 2nd blueprint shows that Door is the one who implements this interface while in the 1st picture, you pass Self as a Target and try to call its function DoorIntact. Since your FirstPersonCharacter doesn’t implement this interface, it obviously doesn’t have this function and so it will do nothing! (Though the ideal case for blueprints would have been to complain about this and throw an error or something).
Introducing a function through interface doesn’t necessarily make that function static and globally accessible! You would still need to call it through the actor who implements it.
To make this work, instead of Self, you need to get a reference to your Door from somewhere and use that as Target. You can also verify that your FirstPersonCharacter doesn’t implement this interface by using the node “Does Implement Interface” before trying to call an interface method with it.
Hope this helps.