Although this has been talked about for a year, Microsoft has now officially confirmed that  July 31, 2021. will mark the end of the Skype for Business Online application. Shutting it down will not affect users of the classic version of the application and Skype for Business Server users.

The popular MS Teams will become the primary Microsoft 365 application for collaboration and communication.
We hereby suggest to all those who started using their Microsoft 365 licenses before September 2019 and are not automatically included in the Teams application, that they start making the transition to MS Teams.