any idea what error 3503 is?

The server error has been fixed; simply restore through iTunes as you usually do and all will be good.

Mine restored through iTunes today, it didn't yesterday. No third party stuff, straight Apple.

did you have an icloud backup? the error seems to have been on the apple side and now should work with a simple restore.

i have same issue with my iphone 6 plus. today i trying to upgrade ios 11. i update my ipad and another iphone without any problem. but my iphone 6 plus still on ios 8.4 error like u. i dont know how to fix it. pls help me if u fixed this error.

I have similar problem with my iPhone 7, iPad mini 4 and iPhone 6S. I think it's problem of iTunes not been able to connect to update/restore server. Best to try on another computer just in case any program installed or virus is working in the background. Try your own solutions 'cause this guys don't know ****...

I'm having this problem too, which is weird because I was able to restore it just yesterday. Did you do an icloud backup right before trying to restore? Because that's the only thing I did differently today and am now getting the 3503 error. I've reinstalled itunes, tried different usb ports, and put my iphone in recovery mode but I still can't restore it.

I have the same problem today on September 24th. After I wanted to restore my ipad air 2, I am stuck with the Itune screen and the white cable and the arrow and an error 3503 not listed .... Not the only one to have this problem. Hard reset (Home button + power) does not work.

J'ai le meme probleme aujourd'hui le 24 Septembre. Après avoir voulu restaurer mon ipad air 2, je suis bloqué avec l ecran Itune et le cable blanc et la fleche et une erreur 3503 non listé.... Pas le seul a avoir ce probleme. Le Hard reset (Home button + power) ne fonctionne pas.

It is obviously an issue today

i am just trying to do a force update , I already have iOS 11 on both IPhone 6s Plus and IPad Pro 10.5

but I am thinking I may have some bugs so instead of going straight to factory restore I am doing a update of iOS 11 but I keep getting ERROR 3503

so I think there is an Apple update server issue

let me know what you guys think

i got the same error again n again, i downloaded the latest version of itunes n did a hard reset n put my phone into recovery mode. i then tried to restore my phone, whenever it's done extracting files, error 3503 will pop up

Can also report from the UK getting this error. 3505 after trying to restore. iPhone 7 32GB

Apple chat has no idea of this error code existing.

Thought i was going insane and thought I had bricked my iPhone.

I've chatted with them twice. Advised me that they had never seen this error code before, and I had tried everything prior to try and restore. I'm sure they've logged it so hopefully due to many people getting it can be resolved.

They tried to set up repair for me but I was going to take it to my repair center tomorrow. Might hang on to see if anyone has an answer.

I'm getting the same error. In chat with support. I've tried updating and restoring on both a PC and Mac, with no luck. Get 3503 on PC and the mac just gets stuck indefinitely till we force it to restore mode again. Hoping we all get a fix soon

Have been on the phone with apple support for quite a while this evening. Support said Apple is treating this as a high priority because of how many people they are starting to see this error effect. Ended up speaking with iTunes support people who went though quite a bit a of diagnostics and info to bring to their engineers. So hopefully we should be hearing a solution in the next day or two.

I am also having this 3503 error code problem on a brand new iPad Pro. I have had no problems at all with iOS 11 on 2 phones, an iPad mini or an iPad Air. Tried to restore on 2 different computers and got the same code. After several hours on the phone with Apple on 3 different conversations, they basically do not know what the problem is and all of the issues started today. Apparently it has been escalated to engineering and they are supposed to get back to me tomorrow. 😕

Same problem this evening. On Windows 10, iTunes 12.6.1.25. Tried updating iPhone 5 from iOS 10.3.2 to 10.3.3 through iTunes (not OTA), so I could get the downloaded update file on the computer. The file downloaded fine, extracted fine, the phone auto backed up, but after that the 3503 error window popped up.

BUT, I had success on Mac El Capitan, iTunes 12.7 this morning. Updated an iPhone 6 from iOS 10.3.3 to 11.

Waiting for a solution on this thread...