They're probably just fine. You can try chirping at them and see if they answer you back, but even if they don't I wouldn't start to worry about it until after day 22 or 23. It's a lot of really hard work to get out of an egg, and chirping uses up energy so they won't chirp constantly in order to save some of that energy for the actual hatching. They also aren't likely to be active the entire time, maybe they're just "sleeping" and resting up for the big moment. Chicks do take breaks during hatching to rest and regain some energy as they struggle to get out of the shell.