Block One Person Facebook

They've either got you blocked or your profile somehow doesn't fit into the group they are allowing to see their stuff per their privacy settings.

Understand a few things: Facebook is the biggest a/b tester on the planet. They are constantly changing what they show you and how they show it (layout, algorithms, etc.) because they are constantly working to maximize the profit they get from advertising.

They are also terrible at privacy, with confusing, contradictory settings that they roll out poorly and never explain properly.

You are right. Somehow they have something set. It is only one post though. All other public posts are visible. But what is weird. Is that post is also listed as public to others. If you block one person, your post automatically changes to friends only not public. At least that's what I have found.