Unable to send alerts using custom webhook in the scheduled interval from Kibana, but test message works

Hi Team,

I have configured a monitor in Kibana and scheduled it to trigger the action of sending a POST request to a custom webhook every 1 minute. I could connect to the webhook when sending a test message while configuring the action. But the monitor is not working.

Kibana Version - 7.10.2

Can you help in finding what might be the issue.
Thanks in advance.

Can you provide your monitor configuration?