Success Message not working

You have a mismatch between the domain and the WordPress URL, you are using:

https://staging.earthcruiser.com/

However your WordPress URL is set to:

https://earthcruiser.com/staging/

These are 2 different domains and causes the Ajax call to be blocked due to CORS.

If you try using the widget from the correct domain https://earthcruiser.com/staging/, it works properly.