top nav items invisible until mouseover

I’m in the process of building a site which presently has two items in the top nav bar: “Home” and one other, which has 8 items in a drop-down. However, when on the homepage, the second nav item is invisible until mouseover. Likewise, when on any other page, the Home nav item is invisible until mouseover.
I’m seeing this behavior on Chrome, Firefox, Edge and IE browsers.
This is using the HashOne theme, with a child theme (so far, the only modification in the child theme is the copyright statement in the footer).
I tried deactivating all plugins and the problem persists, so it doesn’t seem to be a plugin conflict. Any idea why this might be happening, and how I can fix it?