To my knowledge, Get Actor of Class will only work if that specific actor is preexisting in your level. So, anything other than manually dragging it in or perhaps spawning it via a construction script will not do.
Another possibility is that you forced those nodes together unnaturally. Try drawing out the BP Duel Character pin from your validated Get and recreating the binding. There’s a slight chance that you created the bindings from some other node, deleted it, and just reused the code that followed. Sometimes UE will accommodate node mismatches for a time, then just suddenly stop.