My husband was looking online and heard it could take as long as 28-35 days. So let your hen sit on them as long as she wants. If it gets to being too long, then take them away. When you do, you could open them and see what you find out. (And let us all know.) Maybe they just can't get out, and will need a patient and steady hand to help them. You can learn how to do that online. Easy yet difficult. But worth it in the end if that's what's needed. There's actually a video of a woman helping twin chicks hatch from their egg. She started by giving them breathing holes and then VERY slowly worked her way around stopping every so often. Good luck, and I hope more will hatch for you!