If it still doesn't work, step cut the piston band and see if you can find an oring the same size as the one underneath, maybe one size thicker.
If you can't find one, a husky race tech kit will give you a new piston, band and oring for 150 from oem cycle, you will have to use their valving which I personally think is good.
You can also buy bladder kits, can't remember the place (they sell groovy water pump impellers too) which makes bleeding them way easier
Edit: checkpoint offroad for the bladder.