Are there many people in the room? If not, or for that matter even if there are, they might just not be talking.
To see if this might be the problem, in which case there isn't a thing you can do except wait, try joining a different channel and/or network and see if you can see anyone talking there. A good channel for this, I've found, is the #help channel.
Another way to find a good channel for this, is to get a list of channels, then go into one that has a lot of people in it. However, I would not recommend channels where filesharing takes place, as most of the "people" in those rooms are bots just waiting for people to ask for their files.
If it was your firewall, then I would suspect that you wouldn't be able to connect than blocking you from seeing chats.