iphone could not be updated error 4000

This is a known error and it's not clear why Apple has not addressed it. In some cases, it is caused by an outdated iTunes installation. However, in other cases, this error is caused by a management profile especially if you are using an iPhone that is secured by your employer. There are two ways to go around this. You can update the iOS directly on your phone. If you want to use iTunes to update your iPhone, you will need to disable the management profile by deleting it. Once you finish the update, reinstall the management profile so that your enterprise applications can work. Hope this helps.

Error 4000 is specific to iTunes for Windows which has a bug.

Two choices:

Use WiFi to update instead

or

Temporarily disable your iphone passcode. However this will remove local copies of keychain passwords and remove your cards from Wallet.

After you disable/delete the management profile, restart your phone and disable the passcode. If you do not have a management profile but you have a passcode, this could be the cause. Disable the passcode and enable it after the update.

See this --> If you see an error when you update or restore your iPhone ...

Or this --> iOS update and restore errors - Apple Support

Yes. make sure you update iTunes in case they eventually fix it (though Apple write iTunes for Windows)

Try the WiFi option before the Passcode option

Disagree. . It isn’t an outdated iTunes installation. The latest iTunes versions have the bug. There are only two workarounds and I gave them.