What is error 4000 and what do I do?

You are correct that it is a pain. My workaround is to update over the air. Connect to a stable wi-fi and update that way. It works just fine. I always updating my devices via iTunes, but Windows 10 has made it more and more difficult to do. I've not experienced any issues with OTA updates. I can still connect to do an iTunes backup in addition to the one I do with iCloud daily and I've not had any problems. I still sync my other content, such as music, video, photos, and it all works just fine too. Just the ability to update is affected. Many people have reported this to Apple. Unknown what their thoughts are, but you are welcome to leave them feedback as well, Product Feedback - Apple

Hi there,

Try reading this: https://support.apple.com/en-us/HT201210

LW78

I have seen this posted a number of times in the community. You can try one of these .

• Temporarily disable your phone’s passcode before updating
• Update over the air by going to Settings/General/Software Update
• Download the latest version of iTunes for Windows which I assume would fix the bug that is causing this error.

As of the today the current version of iTunes still has this problem. I've attempted to update three different devices (an iPhone 7, and iPhone 11 Pro Max and an iPad Pro), using three different PCs and three different original Apple cables, and have uninstalled and reinstalled iTunes. Backups through iTunes work flawlessly, but attempting to update gives an error 4000 every single time, unless I disable passcode and screen lock (I've seen reports as from Demo above referring to disabling the passcode, but I've not tried just that), and then it works fine.

On the iPad this isn't too bad, but the credit card and other stuff that gets dumped when you disable the passcode is a pain on my phones. I hope Apple will fix this soon!