Hi @jreason, I have been able to make some progress after my cry for help on March 15th.
I personally did notice a difference in message output between the git bash terminal I was initially running my build command on and a Windows 10 command prompt C:. For good measure, I also ran the expo build command in a Bash (WSL), and separately, from within a Windows PowerShell. My recollection is that Bash, PowerShell, and C:\ seemed to proceed past the point of authentication with Apple Developer Portal and the output messages between these three terminals were consistent (please see my other post on this topic of preferred terminals - What is the preferred terminal for "expo build" on Windows 10 - #3 by surven).
Once I successfully got beyond the point of authentication with Apple Developer Portal, my builds were initially failing with credentials that I set up on my own. I have had successful builds before with my own credentials, so I don’t think the problem was there, but I suspect that the expo code has changed since the 2.6.14 version on which I had those builds.
I was able to get a successful build only after having expo generate the credentials automatically. In the past I have avoided the Apple TestFlight based testing process (because of the added complexities) to get my code to run on my iPhone but was pushed to learn it, since there seemed to be no other way out.
Hope this experience helps you in some way.
Best wishes!