Hi,
I am not sure what you mean by compression ring is everything off of the top of the tube (threaded end) and it will still not come out?

If you do not want to damage the fork threads do not hit it without the top nut in place....leave it on when "tapping" it as mentioned in the above post be sure the frame is secure when tapping other wise you are not getting the force necessary to remove the fork.

2 other things that might help:

1 Turn the bike over and put a block into the top of the fork near the ST with the bike secure give it some "taps" to see if this will provide upper movement and help dislodge the fork.
2. Put more PB into the cavity and wait for a while....if all else fails you know the answer.
Good Luck , Ben