What's the mfg date and how was is stored before you smacked it? Also, what was the temp. you had the pack in after you smacked it? If you smacked it and then kept it at 60 degrees F, it won't necessarily expand the same as if it was closer to 70 degrees. It shouldn't take a couple days to puff out.
If it is older, it could affect how it takes off. Doesn't hurt to make a starter and see if they are viable.