Today my Skype wasn’t able to connect. It simply tried connecting for ages and then it failed.
It wasn’t my firewall and also not a old version, as i updated to the most recent version with no change.

This is the solution that worked for me:
•Terminate Skype. Click End task in the Task Manager to be sure that Skype isn’t still running in the background.
•Open the Run-command by pressing the Windows + R keys at the same time on your computer keyboard.
•Type in %appdata%\Skype and search for tje files named shared.xml or shared with numbers or shared if your file extensions got hidden. Then delete these files.
•After deleting them, open the folder named after your Skype nickname.
•In this folder, delete the files with config in their name (config.xml or some numbers).
•Now restart Skype and login. You will need to reconfigure Skype, but at least you’re now able to connect and login again.

Skype should now work as usual. Have fun chatting!