Iphone locks after updating firmware
Often developers will have released a software update which will improve compatibility or remedy these type of problems.DFU is burned into the hardware, so it cannot be removed.On A7 devices, it generates an Ap Nonce and recognizes APTickets as well, so even in DFU, it can accept an APTicket.Often simply rebooting the i Phone or i Pad, and then trying again is sufficient to remedy those error messages. This is particularly true if the software update server is overloaded by requests when a software update is first released. You can also try updating i OS 11 as usual after some time has passed, or even installing the i OS 11 update manually with firmware and i Tunes if all else fails and you want to get the update installed right away.
Rarely, an i Phone or i Pad may fail during the actual installation of i OS 11 or another software update.
The good news is almost all issues can be fixed with a little troubleshooting effort.