Chance Miller:

Apple has confirmed an issue causing a “small number” of iPhone 18 Pro Max devices on AT&T to lose cellular service.

Apple released software and carrier updates to prevent the issue from affecting additional users, but the company tells 9to5Mac that devices that have already lost service will require a hardware replacement.

John Gruber:

It’s only a problem for AT&T customers. No such problems on Verizon or T-Mobile.

[…]

It’s only the 18 Pro Max, not the regular 18 Pro. The salient fact here is that the only iPhone 18 Pro models that use Qualcomm cellular modems, rather than Apple’s own C2 modem, are 18 Pro Max devices in the U.S..

[…]

I’d love to understand how a software update can prevent existing devices from being affected, but a software update cannot restore service to existing devices that have already been affected.

Joe Rossignol:

Apple and AT&T have yet to disclose the underlying cause of the issue.

Eric Schwarz (Mastodon):

It could be as simple as a power calculation geared towards devices with Apple’s C2 modems.

[…]

The other weird variable seems to be AT&T—out of the three US carriers, AT&T is the only one with a lot of the 3.45GHz 5G band in use[…] Most AT&T MVNOs like Cricket, U.S. Mobile, Gigs-based services, and H2O still use 5G NSA on AT&T and it seems they haven’t gotten the new carrier bundles on 18 Pro Maxes.

[…]

Because of those things, my working theory is that an 18 Pro Max on AT&T was connecting to 5G SA and when it was on that unique 3.45GHz band (maybe trying to hold on to spotty service?), it would basically cook its modem and there’s no fix other than replacement.

Previously:

• iOS 27.0.1 and iPadOS 27.0.1
• iPhone 18 Pro and iPhone 18 Pro Max

AT&T Hardware iOS iOS 27 iPhone iPhone 18 Pro Max