Congrats on your first grow in 11 years! It's a celebration!
Sometimes a seed is just a dud plain and simple. Me thinks you got a dud on your hands there. It's nothing you did wrong. Just like sometimes a baby is still born, right? Sometimes the genetics just aren't there and that's just nature doing what she does. Don't sweat it. Plant another seed. I would not expect that seedling to pop out of that funk. Sometimes they do, but it's very rare.