If your built-in firewall is active, it may prevent you from using LoudHush. A procedure for configuring the firewall can be found here: Configuring the OS X firewall for IAX traffic
The "Trying to register" message is not erased from the screen when LoudHush cannot use (any of the) IAX account(s) you have configured. This is usually associated with a firewall blocking UDP traffic on port 4569. Contact your network administrator if you need help setting up your network.
You can specify a different port in the "Configure Asterisk Accounts" dialog from the Preferences page. Specify the port by appending it to the server name.
E.g.: You would use "asterisk.modulo.ro:6677" to configure LoudHush to use port 6677.