Phone update

Good afternoon, there was such a problem. The phone was not updated to version IOS 14.1.5, there was an error “Failed to install the update. A network connection is required to update [software]. " I tried to reset the "content and settings", but now at the stage of setting up the IPhone displays the message "Activation failed". I tried to connect to iTunes there it writes the same thing. Please help me solve the problem.