Slack App Events
You need to set up event receiver in your app. Go to the Event Subscriptions subpage of your Slack app page. You will get a page like this:
On this page, after enabling events reception by the app, there are two crucial elements that you need to fill:
Request URL - this is the URL in Jira, that Slack will call when an event happens.Â
Use the Event Request URL value from the Enabling Slack Integration page to fill this:
If your Jira's external address is different than the one reported on that page, it is crucial that you enter the externally visible address, otherwise event reception will not work
In the Event Subscriptions section, under Subscribe to events on behalf of users, select event types to subscribe to. Click the Add Workspace Event button to select the message.channels event type:
click Save Changes button at the bottom.