I have below scenario:

User registers on Kamailio server, calls to a number which is forwarded to asterisk through dispatcher, asterisk server answers and sends a text message to the caller using sendText but first message is delivered to client with message "501 Not Implemented" but in the subsequent calls asterisk shows that the text was delivered but kamailio did not detect the message.

Guys, any help would be appreciated, I am using the below mentioned config.

Kamailio version: 5.2