The call schedule by Apple Support WILL NOT, I repeat WILL NOT give you the resolution. Trust me on this, I've been through it, they will just keep on passing it to the next person, even the highest of people did not know what this error was. All they do is Googled for it, like you and me, I mean if you wanna be a Customer Support, the least know your product knowledge to the best of your abilities. That aside, if it's still within warranty, bring it to the Apple store but you have to schedule an appointment first and get all your Vaccine completed. Trust me the apple support does not know stuff and gave me the wrong instruction, yet don't even want to be held responsible for it. If not within warranty, best to repair with a third party or anyone you know who could do it. Because of the charges they quote, might as well get a new device. It will be the same for their authorised repair shops be it the one at Plaza Sing or Wheelock. Someone the update has screwed up the system and if it's not within the warranty, Apple will just tell you bluntly to get a new device cause that is what they do best. I spoke to CS for 3 days straight no resolution, keeps asking me to plug in, CS doesn't even know what is DFU mode, told CS I tried on 3 different computers even on my different MacBooks and on a non-apple computer, results still the same. It is likely you will need to replace the hardware, I will update you, currently, my device is being sent for repair, not by anyone related to Apple cause even the Apple Store people don't know their stuff and you can never get through to them if you call the store's landline, only God knows why even they place a number or that function there in the first place.