What is the server address (as-is in the server list) that you are using to connect? Make sure it's "irc.chat.twitch.tv" and if it's not, update it and see if that fixes it for you.
You might also try getting a new oauth key to use as the password. It's possible that Twitch implemented new permissions that aren't associated with the current key.
Also wouldn't hurt to have these commands automatically performed upon connecting:
RAW CAP REQ :twitch.tv/membership
RAW CAP REQ :twitch.tv/commands
RAW CAP REQ :twitch.tv/tags
That will make sure you see extras, as well as who is a mod, streamer, sub, etc.