We can see it saying “Hello” in preview when you press the button, so it has to be something with either the “self” call from the Get Owning Component or however you are loading in the “Montage to Play.” I can’t see your variables so I can’t be sure how you’re passing around exactly which montage you’re trying to play from this, but I would suspect that’s where the issue is.
Have you tried disconnecting the “Montage To Play” from that node and just selecting the one you want in its place?
This is what my montage-on-button-press nodes look like and they seem to be accomplishing what you’re trying to do. Either way, it’s the next logical step to debugging here, I believe.