Homeoffice with VPN

I have a Problem with my Homeoffice Configuration. My Client (Homeoffice) use PhonerLite to connect with the Workplace. I have the Provlem that the Call is cancel after 30 Seconds. Caller and Called askind and the Call is Terminate from the Asterix/FreePBX System. I use a IPFIRE Firewall with Port forwarding to the FreePBX-PC. Have someone idea whats wrong by me ? Sorry for the bad English. Schooltime was long time ago ;(