Yesterday, Microsoft's Skype application stopped working on my iMac and iPhone. Similar to many other people, I couldn't call anyone, receive a call, or update my online status. I checked Skype's status at Down Detector and verified that the issue wasn't specific to my computer setup.
The bigger issue was that I was supposed to have a call.
Fortunately, there are many internet based communication tools, such as Viber, WeChat, or FaceTime. Our solution because we were using mixed platforms was to connect using Google Hangouts.