Warning, before you do the below steps, write down which iCloud account you have used in your phone's Settings app in the iCloud panel. Make sure you know the password for this by going into iCloud.com on your computer and logging in with that account. If you don't know the password, STOP HERE and don't proceed until you figure it out.
To fix this here's what you need to do (if you don't know how to do one of these steps then google it or use a link I provided):
- Transfer purchases from your iPhone to your computer using iTunes.
- Optional: Delete any huge apps off your phone that you don't use. (Usage panel in the Settings app will show you which ones are biggest.) Transfer all Camera Roll photos & videos to your computer using iTunes or Image Capture and then delete them off your phone. Also do this with any large files in other apps that you might have, assuming you know how to. ***This step is optional but recommended because it will make the following steps go much faster.***
- Backup your iPhone to your computer using iTunes. (Steps are listed at this official Apple site: iOS: Back up and restore your iOS device with iCloud or iTunes). I highly recommend before you do this step, and after you do it, that you make sure your computer's hard drive is fully backed up to an external hard drive (if you're on Mac then use Apple's built-in Time Machine software).
- Optional: Now that the backup is complete, I highly recommend you make a separate backup copy of this latest iPhone backup. To do so on a Mac, in the Finder, option-click the Go menu and select Library. Then open the Application Support folder. Then open the MobileSync folder. Then open the Backup folder inside that. Press Command-2 for List view and look for the oddly-named folder whose modification date is the most recent. That's your latest backup. Copy that oddly named backup folder to an external drive.
- Disable Find My iPhone in order to prevent Activation Lock. Go to Settings app and then iCloud section, scroll down to Find My iPhone, and make sure it's off. (You could get locked out of your phone if you don't do this step. Don't worry, we'll reactivate it later after all steps are done.)
- Go into Settings app, General pane, and do Reset > Erase All Content and Settings.
- Restore your iPhone to factory settings using iTunes. (Steps are listed at this official Apple site: Use iTunes to restore your iOS device to factory settings)
- Now set up your phone as a new iPhone. To do this, when prompted to set up your device, select Set Up as New iPhone and tap Next to continue. Complete the setup assistant on the iPhone, except critically: skip the iCloud account entry!
- Verify that you can make phone calls and send regular text messages.
- Now go into Settings app to the iCloud section and enter your iCloud account information.
- Go into Settings app to the Messages section and make sure iMessage is turned on.
- Also in Settings app go to the FaceTime section and make sure it's turned on (unless you wanted it off).
- Now if iMessage and Facetime are still not working, but they were working before you updated your phone, then go to the Genius Bar and stop doing these steps. You have a real problem. If they are working however, then proceed to the next step!
- Now that iMessage & FaceTime are working, go into iTunes and click "Restore Backup". This can take awhile. It will go much faster if you did step 2!
- Once the backup is restored, verify that iMessage and FaceTime are still working. If not, then you either missed a step or else you need to see the Genius Bar.
- If it's working now re-enable Find My iPhone (if you had disabled it in Step 6 before).
This problem is caused by Apple's update process, and this is the same problem they have had with every update. What happens is that there are activation tokens stored in an SQLite system database inside your phone's hidden iOS system folders. For some reason if those tokens become invalidated by the update process, then the iOS software does not properly delete those tokens, even if you turn iMessage off and then back on again, or even if you remove your iCloud account entirely.
Only by doing the steps shown above can you fix this, because when you set up your phone as new, then those old invalid tokens won't exist anymore, and when you first reactivate iCloud, iMessage, and FaceTime on the newly-restored phone in step 8-12, then your phone will establish fresh, valid tokens for all those services with the cell phone towers. When you Restore from Backup in step 14, iTunes follows a series of programmed commands to restore the data back to your phone. Part of those commands is that it looks to see if your phone already has those new tokens. If it does, and those tokens are associated with the same iCloud account as the one that was active at the time of your backup, then iTunes won't overwrite the new tokens with the old, invalid ones. That way your phone keeps working even after the restore.
However if you just wipe the data off your phone and restore from a backup, without doing steps 8-12 first, then your phone will use the old, invalid tokens from your backup. I view this as a MAJOR flaw in Apple's iTunes restoration process, and I have told them about it on several occasions using official bug reports, but they closed those reports as duplicates and still have never fixed this issue, and never responded. I even personally e-mailed Tim Cook about this problem, telling him that it was a major problem and explaining why their developer bug testing procedure for iOS does not detect this bug.
The reason why Apple's developer bug testing program has not solved this issue is because developers are explicitly instructed NOT to try to bug test the standard update procedure, but instead, they are told to install each beta version onto a freshly-wiped device by following a very strict procedure that is similar to the one I have described above. It was only through following that strict procedure AND adding the additional step of activating with iMessage and FaceTime prior to restoring from backup that I was able to finally solve this issue for myself.
This is not a negative comment but in my opinion Apple could improve its quality control of user experience by getting a significantly large random group of various users to update to the beta iOS over-the-air and see if they encounter these kinds of problems.
Based on my experience as a developer I strongly believe this issue is caused by a problem in the way Apple uses its own CoreData framework to migrate the database containing the iMessage and FaceTime service tokens during over-the-air update procedures, combined with a lack of adequate bug-busting "robustness" code. What their code should be doing is that if the device has recently been updated and yet iMessage and FaceTime do not properly activate after a certain period of time, then their code should automatically delete these tokens out of the database and try to create new ones. If it still doesn't work then it should wipe the entire database they are part of, and build a new one from scratch.
Over the years I have noticed a lot of problems with Apple software related to CoreData databases getting corrupted and the software not having the proper "robustness" code in it to notice when this has happened by detecting unusual spikes in processor usage, application freezes and crashes, etc. When these bad symptoms happen, then these apps like iPhoto and Mail should automatically perform rebuilds on their databases. Search these forums and you will find thousands upon thousands of unhappy Apple customers who have had iPhoto, Mail, iCloud, iWork apps, not to mention Spotlight!! and others experience severe data loss, total crashing of the computer, locking up of the system, etc. etc.
They really need OS X and iOS to auto-detect when they have performance, connectivity, and data integrity problems, and self-diagnose what the problem likely is, and then fix it. It would greatly reduce the load on Apple's support staff and make their products vastly more reliable. Sadly I doubt they will ever read this message, nor will they ever hire someone like me to work for them who is good at finding and fixing deep-level problems. (I've already applied to work there in just this sort of job and they didn't hire me.)
