To fix the error, it helps to understand why it is happening. The most common culprits include:

Sometimes, Error -75 can be triggered if your computer cannot reach Apple's verification servers (gs.apple.com). This often happens if you have used software to block iOS updates or if you have modified your network settings.

Error code -75 in 3uTools is generally classified as a firmware verification or file system error. Unlike hardware-related errors (which often point to battery or USB connection issues), Error -75 usually suggests that the software is struggling to interact with the firmware file (IPSW) or the device's current system state is preventing a clean write.

In technical terms, this often happens when the device fails to verify the firmware image during the "Restoring Firmware" or "Verifying Firmware" stages of the flash.

The error often occurs when the device is in the wrong state.

How to enter DFU mode correctly:

Do not use Recovery Mode (cable on screen) for a full restore unless specifically instructed.

3uTools relies on Apple’s mobile device drivers. If these drivers are missing, outdated, or corrupted, the “iDevice75 link” fails.

The downloaded firmware may be corrupt.