Give it a few minutes - hobbitd only loads the bb-hosts file once in a while and needs to pick up this change first. (You can do "killall -HUP hobbitd" to make it reload immediately).
Then your client needs to send in a report, which also happens at 5 minute intervals - check the timestamp on the ~hobbit/client/tmp/msg.txt file.
That file is being updated.
Checking for connectivity: From the client machine (your firewall), try doing "telnet <your Hobbit server IP-address> 1984" - if it says "Connected to <ip-address>" then the connectivity is OK. If not, then you need to check firewall rules.
Connection is good.
And do check that your client has the right configuration - I've made the mistake myself of having BBDISP set wrongly in the client config in ~hobbit/client/etc/hobbitclient.cfg ...
That is right too.
I even ran a network sniff on the Hobbit server, and see the firewall talking to hobbit.
I am stumped. The firewall is a gentoo Linux system. Not sure what the cause is.