In current Linux version of Skype (126.96.36.199), there is sometimes a problem that group-chats are not shown to the user even is there is an activity in these group-chats which is the user member of.
This means that other people are writing to the group-chat you are member of, but you can't see any messages and/or the chat itself in your Skype client - so you are not able to communicate with them at all.
Open any skype chat window and type following command into it, confirm using ENTER key and restart your Skype.
After restart of the Skype client you should see the group-chats, also this command usually fix the problem that you can't see the history of your messages even if you clicked the button to get the history.
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