Start from scratch.
1. Make sure your computer is connected to the Internet.
2. If you have cellular service, make sure the SIM card is inserted properly and is activated with your wireless carrier.
3. Make sure you have downloaded and installed the latest version of iTunes on your computer.
4. Put your device in recovery or DFU mode, and then connect it to your computer.
5. When iTunes detects the device in recovery, select to restore it
6. When the process is complete, set up the device as new.
Note: I assume you have a recent backup of your iPhone.
09-01-2015 05:49 PM