snail problem

i dont know what is going on.i added a few snails and they have been in my tank for 24 hours and they are not moving. they are not dead because they are attached to the rocks and if you stare at them for a while they will move, but they will not go anywhere. what in the world is going on????
-thank you for your time
they are almost in the exact same spot as they were when i first added them to the tank.

i turned the light on and checked on them last night and they were where they are right now.:help:

thanks