Stop now and verify your account as requested. Failure to do so is willfully preventing you from going forward on many levels...if that means having to repeat effort, consider it a small price to pay for being able to continue working.
I verified the sandbox email- no luck. Same result. I also created a new sandbox email, invited as sandbox tester, and verified before signing in as a sandbox tester on my device. Still no luck.
What of the location of the sandbox account (#1 & #2 in my original post). Is that correct and the documentation is wrong? Or is it an indicator of something even larger out of sync?