Thank you for your advice. I was able to slide a credit card into the slight gap between the lens mount and the cap, I kept forcing it around the edge of the mount as I put pressure on the cap to turn. It finally popped off. A tab on the inside of the cap had broken off at some point and I'm guessing that was preventing it from releasing properly. I appreciate your help!
What are your main needs from a flash ? I have a nissin i40 - which is perfectly sized for X cameras as well as fuji styled dials - however , it can't be controlled by a radio trigger - only optical slave mode