Never use a USB hub or extension for restoring firmware; these often lack the voltage required for stable data transfer. 2. Update 3uTools and iTunes

If you are on a PC, use the rear USB ports located directly on the motherboard rather than the front-panel ports.

3uTools relies heavily on components from iTunes to communicate with Apple devices.

Ensure the device has at least 50% charge. A weak battery can cause the device to "brown out" during the high-power ramdisk loading phase.