Hi Colin, thank you for your question!

Sorry to hear that there are some problems with your background image and our team is happy to help in any way we can.

I looked at the URL that image is loading from and it is different from your website's domain name, so possibly the image was uploaded while you were building the site out in a testing environment.  The URL also specifies using HTTPS, but there are some certificate errors returned when trying to load the asset which is probably why you can't see it on the front end.

Most browsers refuse to load any content that has this type of error, due to security concerns, and resetting your background image might be the best way to fix the problem.  You can reset your background using the Background option in the Customizer by first removing the image and then selecting it again from your website's Media Library.

Hopefully that helps you get the background working as expected and please let us know if there is anything else that we can do to assist you.

For more context, here are screen shots of what my site looks like, and what the preview looks like: