Latest iOS update breaks iPhone's cellular connectivity; Apple offers some options to try
Back during the waning days of July, Apple pushed out iOS 14.7.1 to patch a serious security issue that "may be able to execute arbitrary code with kernel privileges. Apple is aware of a report that this issue may have been actively exploited." In other words, if you still haven't updated your iPhone to iOS 14.7.1, you might want to do so now by going to Settings > General > Software Update.
Latest iOS update breaks iPhone users cellular connectivity
The update also fixed a bug that prevented an unlocked Apple Watch from unlocking iPhone units belonging to mask-wearing users. Since Face ID can't recognize a face that is covered with a mask, the iPhone had been prompting mask wearers to punch in their passcode. To save the aggravation of having to do that, Apple allows an unlocked Apple Watch to be used to unlock a user's iPhone.
Some iPhone users have lost cellular connectivity after updating to iOS 14.7.1
While the update to iOS 14.7.1 is an important one, It also has created a serious issue for some iPhone users who lost cellular connectivity following the installation of the iOS 14.7.1 update. On Apple's Developer Forum and Discussion forum (via 9to5Mac) several iPhone users complain about what happened to them after installing this update that Apple asked its customers to install due to security concerns.
A week ago, a member of the Apple Developer Forum by the handle of "Redbean012" posted that "I updated my software to 14.7.1 recently and lost my cellular data completely. I have tried all the troubleshooting steps and still cannot get it to work." Among the troubleshooting steps he tried was to reset his phone a couple of times, reset the network setting, and insert a new SIM card. He even called his carrier, T-Mobile, to refresh the settings on the carrier end of things, but nothing worked.
Several responses from iPhone users confirmed the issue including this post from "Fuse 1369" which said, "perfectly working 7S - updated to 14.7.1, now it's a paperweight went to the apple store, your phone is dead, but we can sell you a new one for $700 maybe it's time for an android."
Apple's support document suggests things that users can try to get their cellular connectivity back
Apple has posted a support document with some suggestions for those affected by iOS 14.7.1 to try. Apple says that if you see "No Service" on your iPhone or iPad (Wi-Fi + Cellular), or can't connect to a cellular network or use cellular data, Apple suggests that you make sure that you are in an area that your cellular provider covers and attempt a carrier settings update.
Go to Settings > General > About. If an update is available, you will see an option to install it. You can check to see the current version of the carrier settings used on your device by going to Settings > General > About and look at the name following the word Carrier. You can also try removing the SIM card on your phone and replacing it with the same card or a replacement from your carrier.
Apple also suggests that iPhone users unable to connect to their carrier after the iOS 14.7.1 update reset their network settings. To do this, go to Settings > General > Reset > Reset Network Settings. Doing this will also reset previously used Wi-Fi networks and passwords, cellular settings, and VPN and APN settings.
If you can't get this problem straightened out, help from Apple might be on the way. Apple will reportedly disseminate iOS 14.8 which might include a bug fix to reverse the loss of cellular connectivity. The update also could set up iPhone models to work with a new feature. As Apple explains, "iOS now offers a choice between two software update versions in the Settings app. You can update to the latest version of iOS 15 as soon as it's released for the latest features and most complete set of security updates. Or continue on iOS 14 and still get important security updates until you're ready to upgrade to the next major version."