Omeka header image on http vs https

So, having an issue with an Omeka site which loads a header image at http://native-history.sites.grinnell.edu, but does not load that image at https://native-history.sites.grinnell.edu. The secure site URL doesn’t return a mixed content error or anything like that … it just loads the page without that image. Force https redirect is disabled, obviously. We want the version that loads at http to also be the one that loads at https, but it’s not clear to me why that’s not happening.

Off-topic but I love your site. Would you mind sharing what theme you are using?

It’s a custom Bootswatch theme.

Is the image hard coded in the theme, or via a setting?

It is hard coded in the theme.

And the request is HTTPS?

Yes, when the request is HTTPS, the header image does not appear (and neither do the header text, and buttons).

We identified the issue: it was to do with the custom theme coding. The image display relied on an if/then check of the base url. We had it the url formatted as http, so if it was https the if condition was never met. We removed the http prefix and the image began to load correctly on both versions of the site.