Certain apps like Slack and Square only support one webhook per OAuth2 app. This means that manual configuration is required in their developer portal, and it cannot be automated.
Go to the “Event Subscription” settings in the Slack OAuth2 developer platform.
The URL format should be: https://YOUR_AP_INSTANCE/api/v1/app-events/slack.
When connecting to Slack, use your OAuth2 credentials or update the OAuth2 app details from the admin console (in platform plans).
Add the following events to the app:
message.channels
reaction_added
message.im
message.groups
message.mpim
app_mention
channel_created
reaction_removed
star_added
team_join
emoji_changed
Turn Socket Mode off for your Slack app (under Settings → Socket Mode). While Socket Mode is on, Slack delivers events over a WebSocket connection and never POSTs to the Request URL (https://YOUR_AP_INSTANCE/api/v1/app-events/slack), so the trigger silently never fires.
Configure Interactivity & ShortcutsNeeded for the “New Modal Interaction” trigger and the “Request Approval”/“Request Action” actions (their buttons resume the flow via this URL).
Go to the “Interactivity & Shortcuts” settings in the Slack OAuth2 developer platform.
Turn interactivity on.
Set the Request URL to the same URL used above: https://YOUR_AP_INSTANCE/api/v1/app-events/slack.