Issues with VOIP over VPN (no audio) - NEC

[rallylew]

I feel like I’m stupid, as I am trying to accomplish a very simple task.

I currently have two Fortigate 60F firewalls with a properly configured VPN, as my SV9100 phone system at site A is able to communicate no problem with the VOIP phones at site B.

i just acquired site C and it happened to have a Fortigate 60F with Fortiswitch 148-POE, which I had to factory reset as the company had gone out of business and left no documentation.

i believe I setup the switch properly (created a VLAN and static assigned it to the switch, then firewall rules for both internet access and access to the site to site VPN back to site A.  Pings all work, no issues there on either side.  My phones register and appear to work properly except I have no audio on either end of any kind of call across the link.  RTP doesn’t appear to be going through.

The rabbit hole I’ve gone down since has pointed to hidden policies that have to be set through only the CLI (https://www.reddit.com/r/fortinet/s/3Ba3lBNl9B), and ( https://www.reddit.com/r/fortinet/s/XN0UZ2DUN5 )which is odd because I do not see those policies on the firewall rules for the working site to site VPN between site A and B.  Anyways, I seem to recall having to troubleshoot this years ago when I first got the 60Fs for site A and B but I can’t figure out what I did.  I’m frustrated because I can’t seem to find a list of the hidden configured options in the CLI.  I just have to mimic whatever is setup for site B for site C and I should be fine.

I’m willing to provide detailed information and relay specific firewall rules but ultimately I feel out of my depth and am now looking for experienced outsourced options.  Any help or directional guidance would be greatly appreciated.

I’ll come back and update this post when I run further diagnostics on site in about 5 hours.

some other details:

site A subnet: 10.1.1.0/24

site B subnet: 10.2.1.0/24

site C subnet: 10.240.145.0/24

all sites have static IPs and now have the same FortiOS (7.2.11 I believe.)