Microsoft forced Skype Classic users to upgrade from Skype 7.4 to the latest version of Skype 8. Users of Skype Classic are not happy that Microsoft is forcing this update on them. Microsoft has been warning that version 7 will be discontinued starting in November 2018. Users have tried everything they can think of to prevent the upgrade message from being displayed. The only option that seems to work, is to downgrade your Skype to version 7.36.0.101, which does not seem to contain this force upgrade “feature””.”
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-forcing-skype-classic-users-to-upgrade-to-version-8/