Maybe you are just entering the wrong room ;)

I can't choose rooms.

Go to www.flyordie.com then roll down to gomoku.  

After log-in, you can chose the room. :)

If it doesn't let you do that, then instead of clicking on GoMoku, click underneath it where it says "More"

Then it will list the rooms and you can just click the room with people.

in fact, here's the link:

http://www.flyordie.com/board-games/go-moku.html

dope!!