Ten seconds after restarting the camera server, you should see the TX/RX lights on the modem show some activity. If not, make sure you have connected the modem properly, and that Host Mode has been enabled for the camera server.
To verify that the camera server successfully identified and configured your modem, go back to the Modem settings page (with the camera server still connected to your network). Make sure that your modem is correctly described to the right of the Detected Modem: label. If the camera server still reports Unknown after restarting and waiting 10 seconds, your modem has not been successfully identified by the camera server, in this case you may have to specify an Init string by hand.