I read ducks can take 31 days to hatch.
I wouldn't give up yet!
Give them another day or two, if nothing changes they might be gone.
Sorry to say it but, my eggs that looked like that didn't hatch. They had died in the last days before hatch day.
Best of luck!
There is so much that could have happened. None of it your fault either.
Duck eggs are challenging little guys.
The exact same thing happened to me and my 5 mallard eggs. Then, I decided to step it up and just get ducklings from Metzer.
Like I said, give it a couple more days just in case.
Then I would contact Metzer about the experience.
the question is, was the hatching environment bad or were the eggs not fertilized?
fertilized eggs would at least show some level of development, even if the baby dies inside the egg, so if you see nothing, then it's possibly unfertilized eggs, since i'm assuming the temperature of the incubator is at least good. don't know if humidity will make underdeveloped babies.