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Finally, I got it activated on AT&T. I waited 10 seconds on each prompt before tapping on next. I doubt that it really made a difference. :)
 
Tried everything myself and still nothing. ATT said it is activated and of course blaming Apple.
 
Mine says activation pending and that I'll get an email when it's complete. Then it let me set up the phone.
 
ACTIVATED. What worked for me was updating my old iPhone to 11.1, then updating all apps. Then I went back and attempted activation again on iPhone X and it worked.
 
Just got through and activated to AT&T. Somebody finally flipped the switch to spin up more servers!
 
Just called AT&T, give them your IMEI and the ICCID and they will activate it. It works!!!
 
One hour of "try again" over and over and over and over again. Finally got it to work.

At some point in the past hour I restarted both phones and turned of find my iphone in settings. Not sure if that was relevant to it eventually working.

I have verizon.
 
I had this happen to me with Verizon. I had to do “start over” when hitting the “off/lock” button. It worked on the second time...
 
Finally.... when I got to the screen that shows my phone number, I plugged it into my computer and iTunes was able to go through the rest of the activation process...
 
Mine finally went through; I don’t know if it was just coincidental timing but it was the first time I tried “manual setup” instead of the automatic route.

I was actually on the phone with AT&T on my old iPhone when suddenly the activation worked and the call dropped.
 
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