Webhook Integration

Hi Team,
I have integrated ES-7.17.6 with Searchguard. However, during webhook integration, I am getting the below error.
Web hook returned error: HTTP/1.1 400 Bad Request\n\n

My alert is as follows:
Match condition on metricbeat condition is WHEN average()
OF system.cpu.cores
OVER all documents
FOR THE LAST 24 hour(s)
IS ABOVE 0

Please assist.
//Ankita