Hens will lay when they're ready, if they're getting what they need, and not being pestered to death by too many randy young cockerels. If they aren't laying, it's because we've failed to provide something that they need. Just because we sometimes also fail to figure out what the problem is, doesn't mean it's the hens' fault.
Here's what I'd try, and has worked for me:
They could be too short on daylight. Put a light on a timer, to come on at about 4 am.
You might also increase the protein a tad. I do this by adding distiller's grain to the layer ration. You can also supplement the protein by adding dairy products, meat products, or a little dry dog or cat food. To avoid feeding them chicken in the pet food, you could buy a lamb meal and rice formula.
You didn't say if they were also getting scratch or other feed. Too much scratch grain or other treat will lower the overall protein in the total diet. What they were eating before? If they were on a lower protein pecentage, it may take a few weeks for them to start laying.
Do you have any roos? If so, how many? If you have too many roos, the hens may be stressed and harassed, that will definitely lower production.
Finally, they could just be laying where you won't find the eggs. I go through that a couple of times a year, everybody decides to lay eggs under a brush pile, or out in the woods somewhere, etc. They might be laying eggs outside in an unknown location(s). Try leaving them closed up in the coop until afternoon, (or for 2 or 3 days) so most of them will have already laid, if they're going to.
Sometimes, if you build some nice new nest boxes, they'll start using those instead of laying all over creation. They seem to be intrigued by new nesting arrangements, and they like them to be changed around now and then.