Since you’re using IP authentication, this should be as simple as you can imagine.
Make sure the Firewall is forwarding all of the 5060 traffic from Flowroute to your PBX. Check this using TCPDUMP on port 5060 of the PBX.
If the traffic from Flowroute is getting “to” the PBX but not being processed by the PBX, check the Integrated Firewall and make sure that all of the IP addresses from Flowroute are correctly identified. Restart FreePBX to reset the Integrated Firewall. Check the 5060 port again and make sure that the traffic is getting in.
If you see the traffic showing up in the /var/log/asterisk/full file, the problem is in your inbound route configuration. Hosts that are not correctly identified in the firewall will show up as “anonymous” connections, telling you that your machine will reject those (since “Allow Anonymous” should always be set to “No”).
To be clear, inbound has almost nothing to do with outbound. If you have ANY outbound connection and have correctly identified the Permit hosts (which it appears you might have) in that config, any traffic from those address blocks will be allowed as valid (not anonymous) traffic.
This is two different problems. Note about firewalls (which I include just because I love to type): traffic that shows up in a tcpdump scan on a port is happening BEFORE the firewall, so if you see the traffic on the outside of your firewall and not the inside, it’s the firewall that’s messing you up. Same on the PBX - if you see the traffic on the Interface of the PBX but not in the logs, it’s the Integrated Firewall working correctly and blocking the traffic.
At the level of networking we are working with, there’s no “accept”. If the traffic makes it to the PBX server, the PBX server is either blocking it in the Integrated Firewall (possible) or it’s being misdirected to some other device. Also, the two conditions you describe are two completely different issues. Not “receiving” means that the traffic isn’t getting to the PBX, which is a problem with your firewall or network. Not “accepting” the traffic means that the traffic is getting to the PBX and is being rejected, either actively (through a “no way, go to heck” message back) or passively (through the Integrated Firewall).