No it doesn't. As I previously stated in this same topic, I can connect fine with that error.
A simple google search got me the answer as well.
Commands you can send
Most normal chat commands like /timeout, /ban, /clear are sent with periods in place of the forward slash. For example, to ban the user "xangold", you would send ".ban xangold" to the server (minus the quotes).
Note: Lines prefixed with < are sent from client to server, and lines prefixed with > are sent from the server to the connecting client.
If you send an invalid command, you will receive a 421 numeric back:
< CAP REQ :multi-prefix
> :tmi.twitch.tv 421 you CAP :Unknown command
A brief list of commands supported by our IRC server include
If you actually bothered to read the OP he's not asking how to connect to twitch, he was asking why he couldn't see users in channels anymore.
And it got resolved. No need to post false information anymore.