1, try to select "Settings" (Settings) - > "general" (General) - > "reset" (Reset) - > "reset all settings" (Reset
All Settings), see if you can solve the problem. The user may need to set up a few more of the iPhone, but any data and photos of the user will not be deleted.
2. Some users found that this problem was caused by past backups. If you restore the data of the backup old model iPhone to iPhone 6 and 6
Plus will cause this problem. Users can try to restore factory settings and set up iPhone 6 and 6 Plus artificially like new mobile phones, which can solve the problem.
3, if the problem is still not solved, it may be a hardware problem, the user needs to contact with the apple, or to the apple store for testing. If it is really a hardware problem, Apple should replace the new machine for the user free of charge.