Hoping things go well for you! Do you mark your air cells? For me, when the cells quit growing it's the first indication that the chick has quit.
I mark on day 7, 14 and 18. If nothing is going on, I'll candle again and look for draw-down, when you see it, things are getting closer!
Are they shipped eggs or local? Shipped eggs are such a gamble.
Is your incubator in a draft free place with a stable ambient temperature? Styrofoam bators are notorious for temperature swings from day to night if your room temp changes.
Are your vents open? Eggs need oxygen.
Good luck -...