Thank you for the update. In your case, it sounds like the firmware on your iPhone 6s has become corrupt. The resolution in your case is to restore the firmware.
You will have to restore the iPhone to a base firmware install, which will erase everything on the iPhone, but you can later restore the contents of the iPhone to a backup that you have on the computer (the same computer you used in the past to sync the phone with):
- You will need to have the iTunes application installed first. If you do not have it, you can download it for free from the following site: http://www.apple.com/itunes/download/
- Connect the iPhone to the computer that you have been using the phone and iTunes with.
- First, you should make a backup of the iPhone through iTunes. Once that is complete, continue below.
- Now it is time to restore:Option 1:
In the Summary tab, click Restore and follow the prompts. (THIS WILL ERASE everything on the iPhone and make it just as it was when you first purchased the phone).Option 2:
Click the button on the top right of the iTunes window for your (iPhone) and then click the Restore button.
- Once that is complete, right click the iPhone listing in the left panel of the iTunes window
- Choose "Restore from Backup"
- Choose a backup date and restore.
Now your iPhone will be back up and have all the restored information from your last sync.
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Thank you again,