I finally called Apple Support and resolved my AppleCare One problem. It is as I suspected: AppleCare One does not correctly handle multiple user accounts in macOS. This is a known issue. No ETA for a fix.
The solution? Cancel AppleCare One and sign up for individual warranties for the devices that were covered under AppleCare One. These new plans will cost me more than AppleCare One and more than I was paying for the plans they had before I signed up for AppleCare One.
My total loss for this fiasco is that I'm now paying $48.03 more per year than I was before AppleCare One to cover one fewer device. (I would be paying $60.03 more per year if I had not decided to leave one of my devices without a warranty.)
As compensation, Apple offered to let me pick an accessory from the Apple online store for $200 or less. (I asked for a gift card instead, but they said no.) I don't really need any accessories, but I found a $150 Mophie 3-in-1 charger my wife wants to try.
Speaking in as an individual and not for Apple, the support person said they hope there will be changes to the rules of AppleCare One because the support burden since AppleCare One was introduced is not sustainable. (Lots of people are getting these “24 hours to comply" emails and they don't understand why and are upset about it.)
I wish I shared this optimism about future changes to AppleCare One, but until then, my advice remains the same: DO NOT BUY APPLECARE ONE.
To answer this question: https://chaos.social/@uliwitness/115073123116283953
Apple can’t restore my old plans because they are no longer offered (e.g., plans without theft and loss protection that Apple no longer sells) and/or because they were “two-year paid-upfront” plans that they have no way to restore and prorate.
@[email protected] No offer to restore your old plans?
John Siracusa
carozas