Keep a couple things in mind, artificial incubation is hard to get perfectly and rarely as good as under a setting hen. But, chickens have been hatching for millions of years without human intervention. Do the best you can with breeder nutrition, turning, incubator temperature and humidity and...
I think the worst thing I've done is to pull eggs at day 24 and do an eggtopsy. There was a live embryo about to hatch. I don't know what I did wrong but all the rest had hatched at day 21.
I also opened an egg into the skillet and an eyeball was looking back at me. :sick
You aren't an idiot or stupid. Don't beat yourself up. You may have made a mistake but since the others haven't hatched yet, it's possible this one wouldn't have made it no matter what you did.
It is a learning experience. You tried.
That happens. There could be lots of reasons. Temperature, turning, humidity, heredity, breeder nutrition, age of breeders and on and on.
What day were they on when the one hatched?
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