Reflashed GoPhone 640 LTE re-flashed to 8.1 cannot sign in to Microsoft account

[Luxion]

Hello,

My WPTweaker changes somehow survived my initial upgrade to Windows 10 through Upgrade Advisor app but broke when I switched SIM cards in the phone.

I know Interop Tools can do what I want but it was crashing when I would go to the parts of the registry I was looking to change. Per advice on Interop Tools creator I started to re-flash 8.1 so that when I rolled forward I would have a clean Windows 10 environment - no remnants of WP Tweaker.

The flash process seemed to go OK via Windows Device Recovery Tool but when the phone boots up it is unable to complete the sign-in for Microsoft Account and therefore no ability to download Upgrade Advisor and complete the process I am familiar with.

I have tried all known fixes for the 8.1 error message - most commonly caused by system date/time issues. Should I give up and adopt some brute force method of loading Windows 10 straight to the phone? It is so weird and frustrating, as though some kooky server in Redmond is denying access for no apparent reason.

Thanks,