After upgrading OSX to Yosemite and Skype to 7.7 (335), Skype gets stuck on "Signing in..." when starting.
It does sign in, as Contacts > Add Contact forces the main window to open, but "Signing in..." never goes away.
Already tried, but didn't work:
Signing out, quitting ("Signing in..." stays even when signed out), then signing back in.
Everything on the Skype support page for Why can't I sign in to Skype for Mac OS X?.
I'm using my Microsoft ID to sign in.
Following the @Buscar advice I used
nettop in terminal to monitor Skype connections.
After quitting Skype, I see 3 connections still there about 20 seconds after quitting. Two of them use port 443 (status LastAck and FinWait1), the other is on a high port (12k+), status FinWait1. Last one to go away is to blu403-m.hotmail.com:443 with status FinWait1.