Here is a solution for Skype group chats are not showing in ubuntu 14.04 and skype 4.3.0.37

Skype group chats will not work on the current version of Skype (It is a known bug reported on their forums for Linux users & other places). You can voice talk, but typing something or having actual access to the chat will not work.

I have encountered the same problem and I found the solution in Skype forum:

To solve this  issue, type below command on any chat window:

/msnp24

after that hit enter and logout once and login again now you will able to show all your group chats.