Why: You're calling '{fn}' on an object that doesn't have that function. The function may have been deleted, renamed, or moved to a different class. UE5 can't bind the call at compile time.

Fix: Check the target pin's type. Search the Content Browser for the actual class name + look for '{fn}' in its functions. If found, drag a fresh reference and use the proper context menu Call Function path. If gone, find a replacement function or use an Interface call.