Chat Commands over IRC has been deprecated and removed https://discuss.dev.twitch.com/t/deprecation-of-chat-commands-through-irc/40486
The announcement was made in September 2022, with multiple shutdown windows, and the final shutdown of chat commands over IRC was in Feb 24th 2023.
If you wish to ban or timeout a user from your bot you have no choice but to use the Ban Users API endpoint.