iTunes error 3503 (updating to iOS 11)

I had the same problem when attempting to update my iPad Air 2 using iTunes (12.7.0.166) on Windows 10 (tried uninstalling/reinstalling iTunes, considered downgrading iTunes, saved a new hosts file as directed by Apple Support pages, even used different USB cables in case the issue was from using an aftermarket cable...) and the ONLY way I was able to get my iPad out a perpetual state of the 3503 error was, sadly, to use a Mac. The software update and restore to factory settings (only option by this point) all went fine, and after I was able to restore from a backup saved on my PC earlier in the day.

The biggest difference I noticed was that the Mac actually DOWNLOADED the 2.34 GB Software Update (which took almost 20 minutes), whereas on my PC, iTunes was proceeding straight to "Extracting Software" without any obvious download to my hard drive happening.

Side note, I did not try doing a WiFi update because I did not have the necessary disc space on my iPad, but I suspect (as someone else has mentioned) that it would have worked fine as it would bypass the "Microsoft" factor.

Hopefully Apple fixes this soon, it already sounds like it is popping up for a lot of people.

Try If you can't update or restore your iPhone, iPad, or iPod touch - Apple Support.

Or try DFU recovery: https://www.payetteforward.com/how-to-put-iphone-dfu-mode/.

Or try restoring on a different computer if you can.

Failing that perhaps a visit to an Apple Store Genius Bar.

tt2

I had this problem also with my iPad Air 2. I solved it for myself after trying the many suggested posts here and elsewhere.

Not sure what caused it, but I suspect it was not deactivating Find my phone before trying the update via iTunes.

I deactivated find my phone from the internet.

I had the previous ipsw for 10_3_3. I copied the 10_3_3 into the place where the ipsw files reside and deleted the 11_0 ipsw.

Plugged the iPad back in using iTunes and I had the option to restore to 11_0 which I chose.

ipsw was downloaded again. The install went fine this time.

All good now.

Worked when doing it over WiFi vs iTunes

I used Win7 just becuse I didnt bring my mac with me, so I updated my iPad air 2 and it worked just fine, when trying to update my iphone 6S I received the same error. So then I tried over wi-fi and it worked just fine.

I successfully updated my iPhone 6 this afternoon. When I tried to update my wife's phone, which is identical, I get the 3503 error. I poked around and found the error in the log files in the directory below. Hopefully that will help someone who knows more than I do to figure it out.

C:\Users\Owner\AppData\Roaming\Apple Computer\iTunes\iPhone Updater Logs

this issue involves the apple servers too, many 401, 403 errors...

Failed to personalize the restore bundle: You are not authorized to make this request. Please check your device or credentials

Depth:0 Code:3503 Error:Failed to copy preflight options during recovery mode restore

The file iPad_64bit_TouchID_11.0_15A372_Restore.ipsw exist nearly 2,5 GB and looks good,...

I think, apple will fix this in the next days,....

Same problem here, on windows 10 and latest iTunes version (iphone 7 plus). Trying to clean install ios 11, and error code 3503 prevents it. No reference to error code 3503 anywhere from Apple documentation.

Today i tried to upgrade ipad to ios11 , and i have this error too. I can't find how to fix this problem on the apple support website, could you please tell me here if you find a solution?

same problem on a iPhone 7plus

Same problem here. Apple chat Adviser had no record of the error code.

Occurring for 1 of 2 latest gen iPODs. On with support now. No answer for the past 15 mins....

same problem on my iPhone 7plus, I have no idea for this.😢