If you use an iPhone and have not yet upgraded to IOS 12.1.2, don’t do the upgrade!
There have been widespread reports of a variety of different and serious problems associated with 12.1.2. If you have “Auto update” turned on, turn it off immediately so your phone doesn’t download and install the update by itself.
If you already have done the update and your phone is working fine, good. The majority of phones seem to have no problem with the update. But so many reports of problems have been coming in since Apple began pushing out the update two days ago that I’ve been telling everyone I know with an Iphone to put off installing the update until Apple figures out what is going on and fixes it.
The biggest problem seems to be the loss of access to cellular data, which means the phone can no longer communicate with the internet. Other problems including WiFi connection problems have been reported as well. At the moment no one seems to know exactly what is going on or why some phones have been affected and others haven’t.
Apple is supposedly working on a fix (IOS 12.1.3) but no one knows when that will be available.
My general advice to most people is that while Auto Update is convenient, having it turned on is a bad idea because of issues like this. You should never do an IOS update as soon as the new version is made available. You should always wait at least several days before updating to make sure there isn’t something wrong with the update.
There was nothing extremely important in 12.1.2 in the first place. Reports I’ve seen indicate that this update was primarily an attempt by Apple to get around an injunction in China preventing the sale of iPhones because of a patent lawsuit they lost to Qualcomm.
If you’ve been hit by this problem, I’m afraid I can’t help. You need to scrounge around the internet and see if there are fixes available. Or if you have an Apple store nearby, talk to them. If you got your phone from a specific carrier, talk to them about a possible fix.
Here are some hints to help you keep from having problems in the future:
Have an iCloud (or whatever Apple calls their cloud data storage feature these days) account and use it to automatically backup your phone. Then if something nasty happens you can fairly easily restore the apps and data stored on your phone.
Turn AutoUpdate OFF. Wait at least several days after an IOS update it pushed out to make sure it doesn’t have serious problems. Install it only after you’re sure it’s bug free.