The only thing I can recommend at this point would be to do a factory data reset. I would not restore from a backup, but start fresh. As soon as you reset your phone, sign into your WiFi and the update should be available for OTA download and should install. Of course, the reset will wipe any pictures, music etc. you have stored on internal storage. If they're on an SD card, that's OK. Make sure your contacts are saved to your Google account so you can import them once you reset. Like I said, in my case it was the Nova Launcher that caused the update not to match. You may have installed some app that changed a system file. Anyway, unless someone else has a suggestion, a data reset is the only way I know that should work.