X-Lite clinet Not registering to Switchvox demo

I can get x-lite and sjphone to register and work fine with other sip servers. When I try to register either one of these soft clients to the switchvox demo I receive a 303 error regardless of how I manipulate the settings. I am trying out switchvox demo and am using external sip clients as mentioned.

Please help me so that I can move forward with Asterick…