Hi Armlocker,
When I first got mine I had no idea it stayed closed up for so long. It turned a very ugly ashen gray and I was real sure it was dead. I was just about to take it back to the LFS when I read on this site that they sometimes take awhile to acclimate. One or two days later it dropped its slime film and opened fully. Been fine ever since. If I remember right it took about 7 days to open.
Hang in there, they can surprise you!