That DEN-JFK flight should have lunch. Looks like you're referring to DL532 which is normally operated by an A321 so you should have pre-order. If you're outside 7 days from the flight you can't order... it only becomes available inside a week.

Also if they have a 321Neo scheduled for equipment, then there is no preorder, although you still get a meal choice but only on board when they come around to take orders.