It’s day 33 of hatching and my mallard duckling hasn’t even piped yet. When we try tapping on the egg shell, we don’t hear a chirp or anything. When we try candling it, we don’t see movement. It also has a black spot inside the shell that has been there for a few days now. We had another egg hatching which had a successful hatch with some assistance. The day that the one duckling hatched, I had came home and the incubator lid was off. The duckling that hatched was fine, but I’m not sure how long the lid was off for and unsure if that’s why the other egg isn’t hatching? The air sac looks good though. In one of the pictures shown below, it shows a indent in the air sac. It’s kind of hard to explain but I hope somebody can help me understand what’s going on & if I should continue to wait to see if the duckling hatches or toss it? Thank you in advance for all the advice & help!!