I know the feeling... I set 6 mutt eggs from my own birds...candled day 7, tossed one clear...candled again day 14...light brown shells; never saw anything but air cells & a dark mass in any egg throughout the entire 3 weeks...no veins, no movement, nada. Having no idea what to expect, I locked down day 19, removing the turner & upping the humidity, & waited. Hatched 3, 1 DIS, 1 never developed.
Had never hatched chicken eggs b4, but I had nothing to lose except time & a little electricity, and it was a valuable learning experience. Now I've got to figure out how to get 3 growing chicks out of my basement & into an outside coop/run separate from the grownups b4 the weather gets too nasty. Looks like dog crate time.