can you post your config? Make sure to remove passwords
also if you can post your debug from these commands:
debug sip stack messages
debug voice verbose
debug sip cldu
I have the same problem, did you solve it ?
Do you have "media-gateway ip primary" in interface config mode on both the interface where your phones are connected and the one to which the SIP server is connected? If not, do that.
My problem came from FreePBX. it doesn't response with the right IP address.
NetVanta : 172.20.172.1
FreePBX : 172.20.172.2
11:17:04.835 SIP.STACK MSG Rx: UDP src=172.20.172.2:5160 dst=172.20.172.1:5060
11:17:04.835 SIP.STACK MSG SIP/2.0 100 Trying
11:17:04.835 SIP.STACK MSG Via: SIP/2.0/UDP 172.20.172.1:5060;branch=z9hG4bK-159e4-547242c-41049e84;received=172.20.172.1;rport=5060
11:17:04.835 SIP.STACK MSG From: "xxxxxxxxxx" <sip:email@example.com:5160;transport=UDP>;tag=52a57570-7f000001-13c4-159e4-e803db73-159e4
11:17:04.835 SIP.STACK MSG To: <sip:firstname.lastname@example.org:5160>
11:17:04.835 SIP.STACK MSG Call-ID: email@example.com
11:17:04.835 SIP.STACK MSG CSeq: 1 INVITE
11:17:04.835 SIP.STACK MSG Server: FPBX-220.127.116.11(13.9.1)
11:17:04.835 SIP.STACK MSG Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO, PUBLISH, MESSAGE
11:17:04.836 SIP.STACK MSG Supported: replaces, timer
11:17:04.836 SIP.STACK MSG Contact: <sip:firstname.lastname@example.org:5160> <---- HERE is the wrong IP external.
11:17:04.836 SIP.STACK MSG Content-Length: 0
I change in FreePBX > Setting > Asterisk SIP Settings > External Address.