any idea what error 3503 is?

I can confirm 3utools got my phone unstuck from recovery mode. While trying to restore on itunes just gave me error 3503 over and over again on 3 different computers. I did however reflashed with 10.3.3 instead of 11

I'm iffy about trying to go ios 11 again after having an unusable phone all day yesterday attempting it

Hey, First of all you need to Turnoff "Find My iPad/iPhone" by logging in to apple website from your computer..! then try again.. using iTunes or U3Tools.

This video helps me : How to Fix ITunes Error 3503 IOS 11 Update and Restore - YouTube

Had the same problem and error code trying to update IPad Air yesterday. Was using a PC running Windows 10 and ITunes latest build. The solution was to take it to the Apple Retail store and have the Genius update on a Mac. It worked without a hitch!

Hi Guys,

After have 2 unsuccessful attempts on Win7 and latest itunes 12.7.x.x - I was able to upgrade using Apply imac and itunes through recovery mode. It is also possible that itunes have released a new version to fix this error 3503 as i remembered-version having issue was 12.7.1.88

Iphone 6 plus - update now to iOS 11 itunes 12.7.1.166

Hope it helps you guys too.

PS: Don't us any other software suggested by some one in this forum as it is chargeable and no guaranty of fix.

Chirag

I had the same problem. I tried different internets and computers but they were all window computers. then I tried on Mac computer. then the problem got solved right away. I didn't get the error code 3503.

try restoring on Mac computer. you wont get the error message.

I think it's about not enough room to load the update. I tried to do the update from my phone instead of thru Itunes on my PC and the first try said there wasn't enough room even though I had 2.41 gb open. I removed a couple more apps, retried, and it worked.

contact apple support so they can gather logs from the device. the 3503 error seems to be happening a lot today! Contact - Official Apple Support

correction - the computer that worked was Macbook Air with El Capitan 10.11.5 and iTunes 12.6.0.100.

I did exactly the same and ti worked. Common denominator for failure was Windows computer. Worked fine on Mac and now I am good to go with all updates and no restore necessary.

3utool fixed my problem, nice and easy make sure it is 2.16!

WOAH! connecting to iTunes in recovery mode worked, finally! Looks like Apple got the hint! 😮🙂

Make sure itunes is updated to the latest version, that fixed my issue. Error 3503 is an SHSH issue

I think it might be a problem with my firewall. I found the article below and turned off my firewall and tried restoring again. Itunes is in the process of extracting the software so I don't know if this is the solution yet but so far I havent gotten the error code. http://ituneserror.com/category/itunes-support/page/3503/

I just got done chatting with support for a few hours. Finally was told it is a server issue at apple and their engineers are working on it and would be resolved soon... Just bought an Ipad this morning and now I'm locked out. First Apple product I've owned since the ipod nano, hope they fix this fast.

Firewall sounds like a good thing to check. My hubby had this issue when attempting DFU recovery after updating to 11 failed. Called Apple and they suggested restoring from my Mac which did work. Tried to restore from his backup on his Windows machine after that and it failed again. I had to restore from DFU again and now he's restoring backup from iCloud. We have not tried anything for his iPad Air 2 on his Windows machine but he just set up his iPhone 8 via restore from 10.3.3 without any issues. He found a bug in iOS 11 so they sent him to Tier 2 support where they have been logging both.