Retransmission timeout reached on transmission

Asterisk Asterisk Support
1

I am getting this message:

chan_sip.c:4020 retrans_pkt: Retransmission timeout reached on transmission a98bdfefc765f813527533cd4ca56bb9 for seqno 1 (Critical Response)

What means that and how can I fix that?

Thanks in advance for your help!

2

You are using SIP and you did’t get an ACK back to the final status you sent for an INVITE.

Typical problems;

No valid route back to the caller.

You are behind NAT but haven’t Asterisk how to find your public address.