Skype has announced that it will discontinue support for older versions of its desktop clients, including Skype for Mac.” An exact date for the change hasn’t been given, but the company says it will happen “over the next few months.” Mobile clients like Skype for iPhone won’t be affected by the change.
The specific versions being phased out are 6.14 and older (the current version is 6.18). The change is being made to ensure feature compatibility across the versions of the software in use and enable the developers to continue building on that foundation. The current version of Skype offers several features not provided in older versions, such as the option to send messages to offline users.
You can update to the latest version of Skype by using the in-app option to check for updates or by downloading it straight from the official website.