how long have they been in the tank?
I've also found that my camel backs were more active at night. I don't have a cleaner, so I can't give any input on that. I would suggest to turn most of the lights off in the room your tank is in, and sit back away from your tank, or getting a red lensed flashlight, and just sit back and watch.
If your shrimp havn't been in the tank long, they will hide especially when you come near the tank, so you probably won't see them much for a while.