Definitely follow that link that Kim has left for you. They could be laying outside somewhere in a hidden nest or predators could be getting to them. The birds themselves could be eating them. So you will need to do some determining here to figure this one out.
Make sure your birds are healthy, no bugs, worms or any other health issues that maybe preventing them from laying. Feed a good layer feed and keep oyster shell in a separate tub or feeder on the side. Plenty of fresh water at all times.
Good luck and I hope you can get this solved soon!
Chickens are very inventive you need to look everywhere as this last week I started looking all over and found several nest due to the suaver egg shortage I was having and for a nest of 29 egg's and another of 15 egg's another small one of 8 egg's but the one with over 20 egg's something was sitting on so I let her go and all the egg's I found were boiled for the chicks this weekend ...