I would suggest using a cheap rubber/plastic strap wrench. Do not use one with a metal handle. Carefully unscrew it without applying too much direct pressure downwards. Sometimes two wrenches are handy.
I use these all the time for ports, lights, etc. that get stuck or have a vacuum lock. Very handy tools for your dive kit.
Jack
I use these all the time for ports, lights, etc. that get stuck or have a vacuum lock. Very handy tools for your dive kit.
Jack