I just upgraded to the latest and greatest version of Office Pro Plus (2019), which still includes Skype for Business, and I am having the exact same error I had with 2016 version of the same, regarding inability to sign-in due to not finding a "Business Server". Error Code: KB2566790. Please see screenshot:
This then in-turn causes the following error screens when attempting to create meetings and appointments, (see following screenshots):
What does the sign-in error mean? Will Skype for Business even be around at all anymore after discontinuing? Are we, therefore, relegated to using only Zoom for setting up "Meetings" and "Appointment's in Outlook from now on if we do not want to subscribe to a monthly-reoccurring fee plan in Teams?