Packet does not reach to destination after call Answer

WARNING[1511]: chan_sip.c:4072 retrans_pkt: Retransmission timeout reached on transmission MzJlZGUzMWQ3OWQ3YzBjM2JhNmEzMDRkNmVkZTM3MGY. for seqno 2 (Critical Response) – See
Packet timed out after 6400ms with no response

Have you read the link contained in the message.

This is generally the result of misconfiguring NAT or firewalls, including not telling Asterisk how to find its own public address.