How to fix: This device is not eligible for the requested build

Thankfully the solution is simple and falls into one of two areas:

  1. The iOS version that’s been downloaded isn’t the right one for the device.   go here make sure you pick the right one and download with firefox http://www.felixbruns.de/iPod/firmware/
  2. There’s an entry in your host file redirecting Apple traffic to another location.
In most cases, it’ll be the second option. As a quick test on the machine where you’re trying to do a restore put the following into a web browserhttp://gs.apple.com If an Apple 404 page (page not found) is displayed then you should be good to restore and therefore you should re-download the required firmware, reboot both your computer and the iPhone and try again. If an index page is displayed (like displayed below) then it means you’ve got entries in your host file you need to remove.
Screen-shot-2011-07-26-at-09.14.12-1024x631

The process for removal on Mac and Windows machines is slightly different but we’ve detailed them below:

Mac OS X

1. On your Mac, open your Applications folder.

2. Navigate to the Utilities folder.

3. Open Terminal.

4. Type “sudo nano /etc/hosts” (without quotes) and press enter.

5. Enter your password

6. Use the down arrow key to find the gs.apple.com entries. Once the cursor is in front, make sure you comment out the line(s) by entering # in front of the text.

7. Save the file by pressing CONTROL+O.

8. Exit the nano editor by pressing CONTROL+X.

9. Restore your iDevice.

Windows

1. Press Start, then Programs, then Accessories

2. Launch Notepad or WordPad

3. Click Open from File menu.

4. Browse to Windows/System32/drivers/etc

5. In “files of type:” select all documents

6. Open “hosts

7. Delete all line that have gs.apple.com or similar

8. Hit Save

9. Restore your device