”an iPhone 7 or iPhone 7 Plus that ran iOS 11.2 or later, before December 21, 2017”
So the window is pretty small for iPhone 7/7+ owners to get in on this:
iOS 11.2 was released on December 2, 2017
iOS 11.2.1 was released on December 13, 2017
Those were the only iOS 11.2.x releases before December 21, 2017. If you didn’t have one of those versions installed before then, you’re not eligible for this. That must be why it’s rejecting my information on the claim form. It’s highly unlikely I would have updated to iOS 11.2 in that short timeframe.