I'm running the messenger on a Ubuntu 14.04 system using Virtualmin to configure an apache virtual host.  I first installed on another system which isn't running ssl or at least I installed it on the port 80  side of apache.  It was also a Virtualmin virtual host running Centos.
The first install went fine and all the sounds worked.  I found I couldn't use it from a https site.  Something about serving non secure information over a secure site.  So I reinstalled it from scratch on the secure site.  When I got to the end of the install where it says "test sounds"  nothing happened.  I brought up the Chrome javascript debugger and observed a few errors.  Two of them were 404 errors looking for  .../mibew/install.php/sounds/new_message.mp3 (or .wav, I don't recall ).  I found it a bit odd that the address was not .../mibew/sounds/new_message.mp3, but then I don't know what install.php is doing, so ...
Anyway now that I have it installed and operational it still is silent.  I brought up the JS debugger but it's not showing anything unusual.  I don't see it attempting to access any sound files, but then that may be in a php file somewhere.  
This is not going to work without sound.  Any suggestions would be appreciated.
Thanks,
Jim.