For those facing this challenge with SIP call without sound. If your Jami is behind a router, in addition to what @krishnak wrote above, if appropriate, you might need to either open or redirect port(s) in your router. The list of ports is at https://forum.jami.net/t/which-port-use-jami-application-are-there-risk-associated-on-upnp/835/2
Opening port(s) is a significant security risk, though. So before opening any port, I suggest to first activating only the appropriate audio codec(s). Then test. Details about this in my other comment at https://forum.jami.net/t/sip-call-without-sound/832/27?u=francewhoa