I had to miss chat last night, and will miss again next Sunday evening.
When I come onto chat, I first type my name on top, and press return.
Then, I immediately click the "Finger" button to see who is on. Towards the end of each line, it lists which channel you are on. If you are not all on the same channel, it can seem like no one else is on. Normally, you enter on channel 2; but if the owner of channel 2 leaves, everyone is moved to channel 0.
To change channels, for example, from channel 2 to channel 0, type:
/JOIN 0