I followed the doc and implemented a smart action in my rails back-end. The action run successfully in my app (it’is actually done & there is no error in the logs: the response is a 200), but I see an error message in forest.
As our server returns a 200 with a success message, I should see that success message.
Thanks for providing so much detail about your issue.
In your capture, we can see that the request is displayed in red, meaning that the browser detected an error about it. Can you please check the console to see if there is any error message regarding this request?