A LOT of T-Mobile ID issues as a Home Internet customer

I have this exact same issue as OP noted.  I spoke with a gentelman first and he did not have any ideas about the issue I reported.  After quite a bit of time on hold, the call disconnected.  When i called back, I was speaking with a very nice woman who may have been the same person who @Alex8842 spoke with as she was very familiar with the issues I was having.  She did a few troubleshooting steps to ensure my email address was correctly associated with my account and also verified that both my personal mobile number (non-Tmobile) and the modem's t-mobile sim number were associated with my account.  After a few attempts at troubleshooting she was still unable to assist.  She offered to wait on hold with me for tech support but due to hold times it wasnt viable.  I am now waiting for a call back from the Home Internet Tech Support to speak with them further. 

A few notes:

@kentuck1163, you are correct that the T-Mobile phone number for the modem is provided and we should use that number.  Unfortunately, when trying that in the process, we receive an error which does not allow us to proceed.  It is the same error that OP @mrobrian provided (image below) in his description. 
 

Also, while the process to create your T-Mobile ID via the community is successful in creating a shell of a profile, it still creates an issue with allowing you to access the account details section as you continuously get the error above. 

We shall see what the Home Internet Tech Support people say when I speak with them regarding the matter.  Hopefully positive news to come on tha matter.