Outbound Email with Headers: In-Reply-To, References and more Discussion

Thank you Chris for the great series! I am running into a error though on this tutorial when trying to create a post and have it show on the conversations page. ActionController::UnknownFormat (ActionController::UnknownFormat): the error logs point to the PostController create action where I am using format.turbo_stream. I'm not sure what I'm doing wrong here, I followed the tutorial to this point exactly.