OK. I was able to get thru, via Apple Store app, by about 1:06-08 a.m. MST.
My "Favorited" iPhone X, 256, Space Grey, AT&T (for some unknown reason) was not set up to be a new iUP account (as I had designated as recent as yesterday), indicating I could add Apple Care. Add Apple Care?!? It's bundled with iUP. Uh-oh...
So I backed out, started from scratch, and made it thru to the carrier confirmation page. After about 30-seconds, I received a message indicating Apple was unable to reach the carrier systems to process my order, "but we have reserved an iPhone for you." It continues that I will be receiving an email when it's time to process my order, that will include instructions to complete my order and a return link. I have 24 hours to respond or my order will be cancelled. They gave me an url to check status - which, of course, I immediately did. The only new info there was it listed my actual email address - that I will be checking like a mad man.
So now I wonder if my delivery date will reflect the time stamp from when the reservation was granted or not until I complete my order per pending email.
Regardless, it appears I at least have an iPhone X coming at some point down the road. #neat
Good luck, all!