The threads could be badly pitted. It took an age to get my puller to screw in. Once I got it started it was a few turns in then off, spray with a bit of WD, try again for about 10 mins. Eventually it screwed in. I used my 3XV flywheel puller, same thread, just needed a small spacer (I used an old bolt) as bolt on the puller was a little short. A few taps of the hammer and off it popped
Don't try and use a 2 or 3 leg puller
HTH
Phil M