The theme is most likely looking for the set featured image, so I think you’ll have to go back through your old posts and set them manually for each one…
The same way you’ve added margin-left, you can also do margin-bottom: 20px;.
Or you can combine the properties into one line: margin: 0 0 20px -15px;
Here’s a few things you can check:
- Are the pages published? I’m not seeing any on your site after a quick glance.
- You might want to try switching themes to see if that helps.
Good luck! And here’s a link to the codex article about menus if you haven’t seen it yet: https://codex.wordpress.org/WordPress_Menu_User_Guide
