I just installed a new 3CX server and 60 t42g's across 4 locations. 3 locations have been flawless but they are also all on a 100m fiber ethernet link. Our 4th location has a 20/20m fiber link but not on the ENS circuit so they come in via a PTP VPN. The SIP AGL on our Firewalls have been disabled, each endpoint is a fortigate. On initial setup i just manually set the provisioning url and the phones worked fine. The first issue came when I change some BLF settings. The phones unregistered and would not re-register. I can ping them from the server, and get to the phone's web council just fine. Everything looks fine from what I see but they will not work until I factory reset them and manually put in the provisioning URL. Second time it happened i took the VPN down for a setting change the phones did the same thing once the tunnel was back up. Any Ideas? I am fairly new to VOIP but get the basics. I don't really want to have to reset the phones every time I need to make a change or there is a network interruption. The 3cx logs don't show anything about the phones trying to register, and the phone logs show this: Jan 12 17:58:44 sua : DLG <6+info >  Content-Length: 0^M Jan 12 17:58:44 sua : DLG <6+info >  ^M Jan 12 17:58:44 sua : DLG <6+info >  Jan 12 17:58:44 sua : NET <5+notice>  ===>>>> UDP socket 10.1.1.18:5060: send 554 bytes Jan 12 17:58:44 sua : DLG <6+info >  cb_nict_kill_transaction (id=7)^M Jan 12 17:58:44 sua : SUA <6+info >  ****eCore event0x0002)ECORE_REGISTRATION_FAILURE **** Jan 12 17:58:44 sua : REG <4+warnin>  Register: no responser, server id:0 Jan 12 17:58:44 sua : DLG <5+notice>  Release a terminated transaction Jan 12 17:58:44 sua : APP <5+notice> [SIP] linestatus lid:0, enable=1, tick=0, old_status:1, new_status:3 I'm going to try setting up the 3CX SBC, Forward DHCP so everyone gets the provisioning url and mess with multicast forwarding across the tunnel to see if it helps, but i am open to suggestions. Thanks for your time.