This might not be the ops problem but the following solved this for me. I had used a bunch of firewall rules to block ads. Inadvertently that blocker blocked ke

This might not be the ops problem but the following solved this for me. I had used a bunch of firewall rules to block ads. Inadvertently that blocker blocked key IPs and domains that Skype requires to make group calls and chats. Switching those off made Skype work normally again.