any idea what error 3503 is?

I am having the same problem. I tried updating from iTunes 12.6 to the latest 12.7 and still have the same problem.

My iPhone is a 6S Plus running IOS 10.3.1.

I have never done anything unusual to this phone. No jailbreak or anything else. I've rebooted, reinstalled iTunes, and always get the 3503 error. I turned off my antivirus software and anything else that was running. My HOSTS file has no entries in it.

For all the money i have paid Apple over the years I expect a lot less hassle. in fact, that is the reason I choose Apple, because it is supposed to be easy and stable. I use my phone for banking, phone, messages, browser, weather, and that's about it. This should be easy.

Of course I don't expect Apple to give a **** or reply here, or make any effort to assist me. This is purely a way for me to vent. Samsung Galaxy Note is looking better to me each day.

Having same issue on my iphone 6s plus error 3503...does any one have fix yet?

My iphone when into no boot - stuck at apple logo...trying to update through recovery is giving above error.

Please advise thanks.

Didn't work for me. I tried to install IOS 11 last night via my pc as recommended. After downloading and trying to install, iTunes told me I had to update or update/restore to my iPad (yes I have a backup on my pc). I kept getting this error message - unknown error(3503).

I went through all the recommended steps - downloaded the latest iTunes, pc is up to date, turn off security etc but nothing works. I just tried your suggestion too, that doesn't work either.

***** as I have a need for this device today. My plan is to visit the local apple store now :-/

I confirm that with the software downloaded via the link http://www.iphone-ipad-recovery.com/solve-iphone-stuck-in-recovery-mode.html , my Iphone run again with a simple click on "Restart device".

Thank you very much ZT21!

I have the same problem, although, some people mentioned that on ios, differently than on windows, update actualy works. Is there any people who can confirm ir, i. e. is here anyone who tried to update or downgrade on windows and got an error, whilst on ios it went through?

MESSED WITH THIS 3503 ERROR ALL NIGHT WENT LIVE TO SUPPORT STILL NOTHING TRIED FROM DIFFERENT CPU SAME CODE 3503 SO I CANT UNLOCK MY NEW IPAD ****** ME OFF ENOUGH IM RETURNING TOMORROW AND GOING SAMSUNG.

Thank you so much!!!!! You save my ipad mini 2 from being stuck at itunes logo, problem came after I update my device to ios 11 using iTunes and got error 3503. Thanks to you man for being the best hero. Thank you! Thank you! Thank you!

I had someone in the support chat, she (?) said she can fix this but I'd need to pay 99,95€

This is highway robbery, this was my last Apple product...

But if she says it is possible, there must be a solution...

I'm getting the same 3503 error when trying to factory default my son's locked iphone. We got it from my dad but he doesn't know the password - it was my mom's and she pasted away last year. Any ideas on how I can restore this one? Bout ready to make an 1-1/2 hour trip to the Apple Store.

YES JB you can! its is almost hilarious a Trillon dolar company dont emmend this issue, it should already work prior to IOS 11 launch not today... but hey publicity page looks awesome!! i guess they are cutting cost we miss you steve... no wait there is a solution buy a macbook and keep getting issues like this on it too!!!

Thank you. I spent over 2 hours on the phone with Apple Support, and finally took it in to Authorized Apple Dealer who could not fix it. (http://www.iphone-ipad-recovery.com/recover-ipad-data-and-get-out-of-recovery-mo de.html).

***Your solution fixed it***

thank you

I have been able to UPDATE my IPad Pro 10.5 and IPhone 6s Plus

They we’re both on IOS 11 but I wanted to do a update and reinstall (not restore) the Firmware

I did nothing and it seems to work ok now

i am in London UK

I know this is too late but take a look at google photos. It's a totally free backup. Also use Facebook and/or you tube. You can keep them private if you wish and have a second and third backup. Apple also has the cloud if you don't mind paying.

I have the same problem with my iPhone 7, trying to restore ios11

i have this problem too, tried to update ipad to ios 11