I'd be suspicious that it's not dinner if you can't preorder your first choice main course.

It's still more than 24 hours before departure, so OP should call DL and ask to preorder the meal. Even if you don't receive the email with website link (normally sent out at just after T-70 for those who have already purchased tickets or been upgraded to FC), DL agents can read descriptions of the choices to you and register your selection.