Mikrotik RouterOS x86 5.4.

One provider + LAN. i tried to configure srcnat - it's works fine. Turn on uPnP и SIP helper. But my sip softphone doesn't work. But if the port forwarding 5060 and 10000-20000 to my PC - it works. I need to run softphones for each of the 50 PC . How do I get it?