Thanks.
To the PBX the traffic looks like it’s coming from 192.168.10.1, which is the IP of the firewall at the PBX site.
The WAN site, has a local IP of 10.0.0.0/24, however looking at PfTop in PfSense, this subnet doesn’t appear?
PfSense box 1 WAN = soft phone connection point.
PfSense box 1 > NAT to PfSense box 2 (100.x.x.x > 100.x.x.x - Tailscale addresses).
PfSense box 2 > PBX (192.168.10.1 > 192.168.10.28).