Restore or update from another computer
Try to restore or update on another computer with a different Internet connection. This helps to make sure there aren't issues with your computer that might stop iTunes from communicating with the update server.
Errors 1639, 3000-3020, and 3100-3999 (with the exception of 3194) are sometimes caused by your network settings. If your computer uses a managed network, refer to your network administrator. Proxies, firewalls, and other network security measures can cause these errors. If necessary, find a different network connection to restore the device. For example, if you're restoring at work, try to restore at home or on a friend's computer and network.
Information about products not manufactured by Apple, or independent websites not controlled or tested by Apple, is provided without recommendation or endorsement. Apple assumes no responsibility with regard to the selection, performance, or use of third-party websites or products. Apple makes no representations regarding third-party website accuracy or reliability. Risks are inherent in the use of the Internet. Contact the vendor for additional information. Other company and product names may be trademarks of their respective owners.