Great post.. I had 6 hours in with Product Care folks that did not even come close to this as being a problem..
Turbo Tax 2020 issue - My Spectrum ISP Router had fixed DNS Servers defined. So, I added the primary ISP DNS Server IP address to the PC Network Interface Card (I.e. adapter) DNS primary position. I then used the Google DNS Server IP address (8.8.8.8) in the alternative position. This fixed the problem.
Intuit is using a different name for the authentication server for 2020.
