400 error on Slack webhook from Auth0

I’m trying to setup a monitoring stream which posts to slack if login attempts are failing, etc. I’ve created the webhook in Slack, and the Slack-provided test POST requests successfully generate posts on Slack. However, Auth0 doesn’t seem to be able to post to Slack. The Health tab shows a 400 error with:
“message”: “Bad Request”,
“details”: “missing_text_or_fallback_or_attachments”

or

“details”: “invalid_payload”

I’ve tried setting the content format to JSON Array, JSON Lines, and JSON Object. I’m guessing none of these are the correct format for Slack- is there an easy way to get the data in the correct format to be digested by the Slack webhook?

It sucks that no one from Auth0 responded to this post since April 22.

Yeah, this is pretty surprising. I was expecting this to be “easy”, alerting ourselves about login issues via Slack, but I guess this is just another thing that we need to beg for on the roadmap?