i have tried for months to upgrade. I purchased additional storage and deleted apps. Nothing works. It comes up with an unknown error on my phone with no code and on my laptop in Itunes it comes up with an unknown error 4000
iPhone 8 Plus, iOS 11
Error 4000 is an undocumented error code (at least publicly undocumented). It means that the connection between the phone and iTunes was interrupted in the middle of a sync or update activity. In the past this might have been caused by a flakey USB port, an antivirus or a firewall. However, there is a new cause of this error that is the result of a bug in iTunes for Windows that requires the phone not be locked during the update. So first check your antivirus and firewall (temporarily disable them), but if that doesn’t fix it there are three workarounds for the bug:
Note that this error should only be a problem for updates; if you are restoring iOS rather than updating it should not occur.
Error 4000 is an undocumented error code (at least publicly undocumented). It means that the connection between the phone and iTunes was interrupted in the middle of a sync or update activity. In the past this might have been caused by a flakey USB port, an antivirus or a firewall. However, there is a new cause of this error that is the result of a bug in iTunes for Windows that requires the phone not be locked during the update. So first check your antivirus and firewall (temporarily disable them), but if that doesn’t fix it there are three workarounds for the bug:
Note that this error should only be a problem for updates; if you are restoring iOS rather than updating it should not occur.
error message when trying to upgrade ot iOS 14.03
