I have had this problem for days.  Lacerte could not help at all.  I finally figuered out what to do.  I uninstalled firefox from my computer.  Turned my computer off. Waited 5 minutes.  Turned it back on and installed Firefox.  I used this browser to install Lacerte 2021 and finally it worked.  My Account Management page was no longer blank and I was in.  Why after hours on the phone with Lacerte they couldn't think of that I have no Idea.