voip line pfSense states

I have a very strange problem with registering my voip line from a freepbx switchboard to the TWT operator.
In practice, the freepbx is connected behind a pfsense and occasionally I have to manually reset the states because the voip line cannot be registered to the operator.

The pfSense is configured with the rules of nat of the RTP ports and of the SIP port from the public ip of the TWT operator to the ip of the freepbx.
How can I monitor what the pfsense blocks when the sip line is not registered?

Thank you.

See this pfSense® software Configuration Recipes — Configuring NAT for VoIP Phones | pfSense Documentation

This helped me a lot to get voip perfectly working for me, Specifically the UDP timeout.

Thanks David,
I modified the rules inside the pfsense as shown in the guide and now let’s see if the voip lines remain registered.