Ok I don't know why but when testing it this weekend it was working. I did not change anything neither did I reinstall and fresh setup.
Would this have to do with the static routing that was setup previously but the device it was pointing to was removed the same day it was setup till recently when the client went over to the new system and was installed again. I mean it makes sens that the pbx server was speaking to the firewall and the firewall was pointing to a device on the network that was not available.
NAT is now disabled and siproxd is kinda setup.
I'll arrange to test the DNS rebinding check to disable and the preferred work around and the same for Browser HTTP_REFERER enforcement and get back if it works now. Though the client registration check for the App was an issue even before static routing was setup.
Please let me know if there is clarity needed.