Welcome to BYC!
You might want to check out the learning forum and also search the threads on laying. Hens also put off laying if they are stressed. Make sure they have enough space, no high ammonia levels, etc. They also need additional light in the winter. 14 hours is what's recommended if you do use light but I usually only give 12. They lay fairly well with that and don't get stressed ad much. Good luck to you and again
It's possible that they may be hiding them. I have heard stories about people who find eggs under hay bales, bushes, and even tractors. Have you searched around?