Getting error while integrating Slack with Jenkins

I have integrated Slack with Jenkins. If the job is triggered by someone I’ll get a notification but also I want to deploy the job via Slack. So, for this, I have added the Slash Command app in Slack and configured all the steps correctly but after triggering the command via Slack I am getting this error.

Hi,

This error is a generic message for any failure in Slack. You should check if your Jenkins endpoint, which receives the request to trigger the job, is reachable.