[Theme: Prosperity] Content background not changing to white in light setting

Hiya! I’m having issues with the ‘light’ toggle setting on the dummy site I was asked to troubleshoot. Presumably, this issue is relatively new; there should be a (naturally) white background for the content area containing the posts and widgets, but instead it defaults to black.

The issue seems similar to this one. Is there a section of code that I’m missing in the child theme stylesheet?

Thanks!