Perhaps no one is on the channel because it isn't a channel anyone uses? Or perhaps you're on a network that doesn't have that channel? For example, #Invision is on a few networks, but not all of them. If you tried joining it on a network that doesn't have it, then you'd have an empty channel. You could try a #help channel as that channel will usually have people in it on any network.
The other possibility is that you are connecting to a server that is in the middle of a netsplit and no one else is using that particular server. You might try a different server on the network.
For that matter, try another network and see if it works.
