Can’t change heading colors

I can change text color but not color for the headings. Here is a sample page: https://www.lamppostsites.com/who-we-are/. I can’t change the background either, so both heading text and background are white in the spaces you see.

I’ve tried three different browsers, deactivated all plug-ins except yours, cut all custom CSS code, and still the problem persists.

I started with a clean install of WordPress and GP premium, but I did import a site using All-in-One WP Migration. Still, I had no problems with the site I migrated. Oh, and I converted each page from classic to blocks. Thanks for any help.