Egg not hatching..

[CartoonNinja]

So, I have a small incubator, that only fits about seven eggs. I've had the eggs in there for 21 days, and 6 of them hatched within 48 hours. They were all born with no problems, but I have one single egg hasn't hatched yet. I've been candling it, and it looks healthy and had been properly developing, but still hasn't hatched. All the eggs were from my own chickens so there was no shipping involved. I'm just wondering if I should continue to wait for the egg to hatch and if so for how long.. Also, is there a reason it might not hatch, even though it looks healthy?? Thank you!

 

[Duckopolis]

It may be having trouble pipping. Give it a few more days. It it does not hatch within three more days, it probably won't hatch. Do you have pics of the egg candled?