You may have to shoot it off lol.
What you are probably dealing with is carbon that seized it to the brake. Did you put any kind of lube on the mating surfaces? It's also a good idea to remove it after shooting, but that's not always easy especially if it's hot as f. I know my surefire was hard to remove without even having shot it, so any carbon will add to the difficulty. Have you tried shooting it again to get it hot to see if that might free it?
I would call surefire to see what they recommend, but I have seen on youtube where people have unlocked the locking ring, and shoot a round through it, and the can goes flying off the muzzle due to the pressure. Call surefire.
How did that micro sound? Probably adds almost nothing to the muzzle for about 20db reduction? They seem pretty cool.
Scott