: Skype version 4.0 is over a decade old. Microsoft (the owner of Skype) has long since "retired" these versions, meaning they likely won't connect to modern servers.
If you need Skype but can't (or don't want to) install the full desktop app: Download skype 405 zip
: Use skype.com in any browser. It requires no installation and is always up-to-date. : Skype version 4