I had the same problem. the contact with the grommet and glass is dry. I was able to use a paperclip and run it in between the stem and grommet while it was under water. It eventually broke the seal and I was able to twist the stem. If it's still a problem try using some oil to break the seal. Obviously corn or some cooking oil NOT motor oil or WD40. DOH. Hope this helps and good luck I know that sucs. Next time try using a little petroleum jelly on the grommet b4 u put it back, that helps a little.