Rasa deployment on google cloud app engine

I am currently deploying Rasa on Google Cloud App Engine Flexible. I am using the docker file provided with rasa and creating an app.yaml file for the deployment. But it is not working currently. Can someone point me into the correct direction.

I did as well. I had problems integrating the UI with CORS problem, but slack integration works fine. ATM I have a problem trying to deploy rasa custom actions server. What is your problem exactly?