See also Apple's KB TA38604 Device was not pwned (signature checks were not blocked). Can also happen when there's a problem with the IPSW.i Tunes tried to enter the Restore Mode, but the device turned back to the Recovery Mode.However, it's not so easy if your i Phone only has a small amount of space.

problems updating iphone 4s-21

When Apple releases a new version of i OS it's normally a simple process to update it on your i Phone or i Pad.

We have instructions to do so here: How to update i OS on an i Phone.

However, if all that sounds like a lot of extra work, there is a way round it.

Most of the errors can be found at Apple's Knowledge Base. Some have seen success afterwards by doing the downgrade from DFU mode instead of the normal Recovery mode. This is caused by a failure to match the Baseband Nonce currently in memory to the nonce returned in the Baseband Firmware SHSH blob.

The App you've tried to download in i Tunes couldn't be saved. Use Tiny Umbrella or redsn0w to kick it out of Recovery Mode.

There is a problem with the permissions of the Mobile Application folder. The baseband does not get updated using this method.

Check system time, reset Internet connection, update root certificates. This occurs when the media library on the device is corrupt and cannot be modified or updated.

Permission error either on your computer or the device. Also occurs in restore logs as "unable to convert ramrod 1004." Seemingly caused by a modem firmware chipset malfunction or faulty dock connector, the only fix is to either heat up the chipset or replace the dock connector.

If you experience this issue on a Mac, disconnect third-party devices, hubs, spare cables, displays, reset the SMC, and then try to restore.

If you are using a Windows computer, remove all USB devices and spare cables other than your keyboard, mouse, and the device, restart the computer, and try to restore.

Restart computer; change USB port; reinstall system.