any idea what error 3503 is?

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.

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

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.

Same here...received 3503 on my Ipod touch and then tech support had me plug in my wife's Ipad and now that is stuck too! Was on the phone for 90 minutes and they concluded it was a problem with windows.

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. 😕

No clue what the problem itself it, but i had the same problem when updating my iPad from iTunes on my PC. I then tried updating from my MacBook and it worked and fixed the problem. Looks like it may be an issue with iTunes on PCs/Windows?

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...

I'm noticing a lot of people received this error when updating. I wasn't updating, I updated to 11 on Tuesday. My phone was plugged in on my nightstand and I went to use it a few hours later and it was on the apple screen (it was fine when I plugged it in to charge). I cannot update or restore my phone via itunes. On PC I get code 3503. On Mac it just sits indefinitely "waiting" for the iphone in the restore process. Neither the rep, nor there supervisor were able to help. My phone just keeps randomly cycling between the apple logo screen and a black backlit screen (when I don't force it to the restore screen). Their solution was to schedule me to go to the apple store tomorrow.

I have been trying to restore on my wifes iphone all day. nothiong but issues... Till i signed out of iCloud..... its now restoring... and did the IOS11 update...

not saying it will work for you but maybe?

I too got the error 3503 trying to update my iPad when connected to a Windows system. After reading the 4 pages of the thread, I tried running the update from a different computer (a Macbook Air with Sierra 10.12.4 and iTunes 12.7.0.166) as was suggested in one of the posts and while it seemed to go rather slowly, it did work! My iPad is now functioning again! Good luck everyone!

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.

From what I have seen with it today, it does seem to be limited to windows. It IS NOT The host files, it is NOT your firewall. It may be on the apple's end after all. I can confirm that it is being looked by Apple in high priority. To the comment of Samsung looking better - perhaps, but do they have awesome support? apologies to everyone in tv land having this error - it is being looked at 🙂 I called in as I was having the issue as well and apple engineering is looking into this -- on the EVE of high sierra (10.13) being released tomorrow, my hypothesis is that it has to do with some sort of activation/ restore server. If I had to guess, I'd be on the lookout for a new version of itunes higher than 12.7 - time will tell! If they get back to me, I will post anything I find.

Thank you ZT21, I was stuck with the error 3503, after update to iOS 11, I do read your post and download this software: http://www.iphone-ipad-recovery.com/solve-iphone-stuck-in-recovery-mode.html, and the stuck was fix!!! I hope it help others fix the problem!!! I am so happy to solve mine!!!