Issue natting internal PBX on port 443 on different subnet

Hello Folks.

This is my first question and we have this problem:

My network have 3 different sites. The A site has an UTM v.9,  192.168.x.x. The B and C sites have a 2 RED 10 one in each side.

In the B site we have installed a PBX with a web interface on port 443 - https. The subnet is 172.16.x.x

We need to access from the outside to the PBX web interface that has 172.16.x.y:443

Inside the network i can connect from A site to the PBX, so the traffic seems to be fine.

The port 443 is already used from outside so i have configured a new firewall rules that enable access from internet with port 444 and a DNAT rule that translate port 444 to 443 to the PBX IP address.

I try to connect from Outside but the connection fail. Opening Firewall log i can see that the DNAT rule is applyed (a while line fill the line) but i receive a time out error.

this what the log write.... the RED are configured in Standard/Split mode...

Anyone can support me?

Thank you in advance.

PS: THE IP adderss have been modified randomly