Why can’t I sign in to Skype for Mac OS X after upgrading?
From time to time, we do retire older versions of Skype to focus our efforts on improving the most recent versions of Skype. When this happens, you'll see the following message when trying to sign in to Skype:
If that’s the case, simply click Download the latest version now and follow the steps to upgrade to the latest version for free. You can also follow detailed step-by-step instructions here to resolve the issue and continue using Skype.