You must use SIP proxies, but not gatekeepers 🙂
Indeed, by default Quintum accepts SIP calls from everywhere, not just from the SIP proxies (this can be changed though).
Check if your “outgoing ip routing” option is set to 1 (SIP).
This will tell Quintum to start working with SIP.
Btw, using the debug is always a good idea instead of wondering what and where could be wrong.