The Windows Phone app for Skype for Business is being retired
Skype for Business app for Windows Phone will no longer be able to download from Microsoft Store. Also the app will not be supported.
Instead of building new features for Windows 10 Mobile Microsoft will invest in Skype for Business mobile apps for iOS and Android, as well as desktop applications for Windows and Mac.
Existing users will continue to be able to use it.
Beginning in August 2018, Skype for Business on Windows Phone 8.1 will no longer be available for download.
Beginning in December 2019, Skype for Business on Windows 10 Mobile, will no longer be available for download.