We have resolved the incident and have resumed normal service.
Affected services: Skype-to-Skype calling
Affected products: Skype for Android, Skype for iPad, Skype for iPhone, Skype for Linux, Skype Lite, Skype for Mac, Skype Professional Account, The new Skype for Android and iPhone, The new Skype for Windows, Mac and Linux, Skype for Windows 10, Skype for Web, Skype for Windows desktop, Skype for Xbox One
Affected countries/regions: Africa, Antarctica, Asia, Australia / Pacific, Europe, North America / Central America / Caribbean, South America