I got the below error message when I upload a webhook to facebook:
The URL couldn't be validated. Callback verification failed with the following errors:
HTTP Status Code = 503;
HTTP Message = Service Unavailable
From what I have read, it means the service is unavailable.
I'd like to know if the service is referring to facebook or the host for my case is Heroku.
Hope someone can clear my doubt.
Tks.