URGENT Insecure Content - Logo Image being loaded via http

We're having problems finding a way to lock down our sites running CoursePress. We're using woocommerce to sell courses. When we get to the checkout page, we're consistently getting insecure content warnings.

In the past we were able to just go into the customizer and reset the logo image. Now we are unable to fix the error at all. We have attempted to use the insecure content fixer plugin, but to no avail. It seems that the http is hard coded in CoursePress' theme.

We're not able to sell courses until we get this resolved. Is there something we're missing?