Siemens HiPath through FortiGate firewall

[AnvbiZ]

Hi folks,

First of all, I appologize for my poor English writing.

We currently have a Siemens HiPath PBX (I think it is the 3800 model) communicating to one of our sites through a pfSense. 

We decided to substitute that pfSense machine for a FortiGate 90D, with the same firewall rules and the same IP of course.

After we started to use the FortiGate, we lost phone calls to that specific site. I checked both pfsense and FortiGate configs:

- allow/deny rules are the same

- IP adresses are the same

- routing is equally configured

Also there's a detail, we have a Linux machine with some static routes for that specific site, but they were added to the Forti too.

One strange thing I noticed is that even in the same LAN, this machine cannot ping to the FG firewall, even if we plug the FG to the same switch port where the pfsense was connected, and our switch has no VLANs. Routes were also added to the PBX, and still nothing, phones are dead between those networks, and they only work with that pfsense.

My question is, should I keep checking the FG90D config for a human error or I need to do something on the FG90D to allow these two PBX to communicate without having this Linux machine I mentioned? 

Thanks in advance :)