Remote event receiver not working

I know this is late to answer but it can be helpful to the future visitors who will come accross this question.

The error you specified "The remote event receiver call out failed", it suggest that you are creating an event receiver in SharePoint Online.

Before the event receiver is called it should be hosted somewhere and the sever on which the event receiver service is hosted must be accessible by your SharePoint Online domain and also from your firewall settings.

This error occurred when your event receiver does not able to able to access the url of *.svc file. So make sure that your *.svc file should be accessible.

For more detail information you can see