You’re executing the AttachToActor node on every tick which means that, depending on your system, you are attaching the Boat to the Galleon 60+ times per frame, likely causing it to fail. Optimally you would execute this on BeginPlay or with a Custom Event.
I also noticed you’ve selected “Keep World” as your Location Rule on the AttachToActor node, change it to “Snap To Target” so the Boat actually displaces itself to your Galleon (at the pivot point).