I'm currently experiencing an issue after setting up and integrating a Skype for Business 2015 test environment with Exchange 2019.
I have a windows client with Office 2013 located in the LAN, and on creating a new appointment I can only see "Lync Meeting" instead of "Skype Meeting".
Clicking on the "Lync Meeting" button results in the error appearing in the attached image, even if the Skype For Business Basic client is running and the user is signed in. Lync Meeting Error
In order to integrate Skype for Business 2015 with Exchange 2019 I followed this guide (part 1 only): Integrating Skype For Business 2015 with Exchange guide
Any help would be much appreciated.