Usually, mushroom pins abort when there isn't enough humidity around the block. Don't panic! Your mushroom kit still has all the food needed to produce mushrooms. Simply pick off the dried-up pins, wait one week, letting the block dry out on a plate. Then, soak the block for 20 minutes in cold water, drain all the water out of your kit (species that grow in the bag) and start the process over. If you didn't use a humidity tent the first time then it may be helpful the second go around. It creates a moist microclimate that your block should thrive in.
Take a trash bag or other loose-fitting plastic bag and put plenty of 1/2 inch holes in it. Your mushrooms need to breathe! Drape the bag over your kit and mist the inside of the tent or the slice on your block at least once per day. When you start to see baby mushrooms form (pinning), you can remove the bag and keep misting the block.
Make sure to keep a close eye on the kit. Spray 2-3x daily with water to keep it hydrated.