Hello, I tried many configuration's changes. I never can etablish/register to the SIP trunk provider. 06/10/2017 12:15:07 - Registration attempt for Lc:10000(@peoplefone[<sip:firstname.lastname@example.org:5060>]) is scheduled in 40 sec. Testing 3CX SIP Server... failed (How to resolve?) stopping service... done detecting SIP ALG... failed (How to resolve?) testing port 5060... full cone test failed (How to resolve?) starting service... done We have a Forigate Firewall and i followed the recommendation's from 3CX. Change nothing. Peoplefone SIP provider saying having a problem on 3CX side or Firewall Side. I opened a support ticket at Fortinet. But i would check the configuration of 3CX too.