Successful hatch except for one egg: WDYT?

[daisydog16]

Had 6 eggs incubating, 5 hatched with no real issues, last hatch was 12 hours ago (21.5 days)

This one still hasn't internally pipped. My husband and I both thought was maybe saw a little movement but weren't convinced.

This is now the start of day 22.

Anyway, here's a couple pictures candling the air cell. Thoughts?

 

[TOR]

Put it back in the incubator see what happens.

 

[Tonyroo]

That egg doesn't look right, 3/4 of the egg should be dark with the 1/4 being the air cell. Looks like the chick stopped developing according to the picture before hatch day.