It is down indeed (<a href="http://heartbeat.skype.com/2015/09/skype_presence_issues.html" rel="nofollow">http://heartbeat.skype.com/2015/09/skype_presence_issues.htm...</a> and Twitter <a href="https://twitter.com/Skype/status/645919917510914048" rel="nofollow">https://twitter.com/Skype/status/645919917510914048</a>). Desktop client might be working for some people, and I don't know if the mobile apps are affected too.