Is the mIRC client set up correctly to handle the WHISPER command? The code I was using did not know how to handle it and so just ignored it and didn’t show it as a message. You may need to change something so that it handles the WHISPER command differently to a PRIVMSG command. Can you view the raw logs and do you see anything coming through with WHISPER in it?
If you are getting absolutely nothing in the logs resembling a message using the command WHISPER then I would guess that Twitch is just not sending it to the target user. In which case the whisper needs to be sent all lowercase for the username.
Last week I noticed that some whispers just were not being sent, had to resend it a few times. I think this has been fixed now though.
All chats, main chat and group chat run on the same AWS now, so you can just connect with irc.chat.twitch.tv for all of them. Have you tried using irc.chat.twitch.tv using port 6667 for the 2nd instance?
Have you tested that the CAP REQ :twitch.tv/commands is working correctly? If it is working correctly the client should receive notices like “This room is no longer in slow mode.” etc if slow mode is activated or deactivated.
Hope some of this helps 