If you have two step verification enabled, don’t update your only two authorised devices at the same time!
With many devices, mine, my work’s and my wife’s, to update to iOS 8, I was on the case as soon as I got home from work. The update showed up straight away on all our devices so I tapped “Download and Install” on all of them. Each was saying it was going to take about 3-4 hours, the limitation clearly being Apple’s servers not my BT Infinity which would have swallowed the download in far less time than that.
3 hours of twiddling thumbs later both my iPad and my personal iPhone were ready to update so I proceeded with both at the same time. This was a big mistake.
Both devices reached the ‘verify your identity’ screen, and of course neither was able to provide me my code. Furthermore, my master key was locked away in 1Password for iOS, which was only on my personal iPhone, sync’d to iCloud.
I tried logging into Apple ID on my Mac to add my wife’s phone or my work phone as a verified device but that also required two step verification.
My only way out was to buy 1Password for Mac at a cost of £35, then find my master key. That then allowed me to add my work phone as a verified device and use that to verify me to unlock my iPad and personal iPhone.
I don’t know what I’d have done if it wasn’t for me downloading the latest 1Password for iOS only the week before!