You get the following error if your domain is not yet been authorized by CrossEngage:
XMLHttpRequest cannot load https://api.crossengage.io/api/.... Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource.
In order to fix this, please submit a ticket with a request to include your websites to the list of accepted domains. Once the connection is established, you can get events from all domains you use.