Block background stays white

I have two blocks with white backgrounds and dark text in the hero section of the front page. The text switches from dark to light but the background does not change – which means the text vanishes (white on white). I’ve tried several dark plugins and they all switch this fine.

Your solution is more accessible – with alt text and a menu slider – so I would prefer to use it if there is a way to get this fixed. I’ve disabled the plugin for now but this is what shows in dark mode:

Same thing normally

The page I need help with: [log in to see the link]