I feel like you might have been doing what I was, and if you visit this post Facebook Setup - Webhook not resolving - #6 by ManyChat - then you’ll see how I dealt with a similar situation.
I am also assuming you have credentials.yml already filled out too. After that, you’ll need to fix the endpoints.yml file and uncomment the webhook endpoint. Then run rasa with the following command:
rasa run -m models --credentials credentials.yml --enable-api --log-file out.log --endpoints endpoints.yml