I'm sorry for the frustration.. this is odd.  Can you go to the Start Menu and select ProSeries 2020 -> Tools - Connected Customer?

This should allow you to enter your Customer Number & Zip Code

After that, you should be able to login with any user / password associated with that Customer Number / Zip.

If something along the way isn't working in that sequence, respond here or call into customer support so we can get you going.