Error 4000 while trying to update my iphone to ios 14.1

You get past this problem by removing your PIN-code. I my case this is working, but doing so removes all your registered ApplePay-cards which you have to register again after the update (including bank approvals), which is not really acceptable for each update.

Thanks! Removing device PIN-code does help.

I bumped into dreaded Error 4000 on iOS 14 and 14.1 update.

Hopefully the entire upgrade process would be streamlined while this bug is fixed. The upgrade is slow and constantly interrupted by questions like "Apply, yes/no?".

The officical Apple support worked the problem through with me and ended up doing the update in recovery mode.

This means you have to restart your device into recovery mode (My iPhone: Switch on and hold the side button, press volume up then volume down after the logo appears while continueing to hold the side button. After a while the recovery mode is shown) and connect it to iTunes. Then choose "Update" from the given options and prepare for a long update process. Be aware that this might lead to a factory settings reset (iTunes will give you this warning too) if the process fails.

Doing it this way kept at least all settings (including registered ApplePay-cards) and caused no trouble as far as I noticed. I assume they expected that this procedure would be necessary only once, but on the current update (14.2) I ran into the update problem again.

Thanks for the update. Good to hear Apple is working on the issue.

To me, disabling PIN (with all the negative effects it will have) sounds somewhat less dangerous than the potential factory reset. Obviously, going for a restore is always an option should that happen.