are you using a puller that requires an adapter to go in the end of the crank shaft? Or does the puller have a flat face/surface to mate up against the end of the crank? Some pullers have a pointed end, which would require an adapter to "protect" the crank end.

to use the puller properly, un-screw the center part all the way out. Screw the outer part all the way into the flywheel, getting as many threads in as possible (more threads, better chance to not damage puller or flywheel). Then use the center part of the puller the pull the flywheel off. Some can be very stubborn so get a long handle to get as much leverage as possible to break the flywheel free. Go slow, and it should come out no problem.