Skype group chat not working anymore
You can type these in any skype chat window.

• /dumpmsnp – show details about your connection
• /showplaces – show where you are currently connected

What was happening was that /dumpmsnp command was showing “LoggedOut“, but I was online and talking almost normally (except group chats).

System: MSNP: Connection Data:
 * Status: LoggedOut

 
To solve this “LoggedOut” issue, try this on any chat window:

/msnp24

and restart your Skype.
After restarting, /dumpmsnp output shows the following status:

System: MSNP: Connection Data (MSNP24):
 * Status: LoggedIn

Source : Skype community