Hi Paul,
Okay, so I see most of the posts belong to almost every category there. The way the category filter works by default is that all of the checked categories must match, and any of the unchecked are excluded. In most cases this is an expected behavior, but in your case this is not desired.
I have changed the terms logic to ‘At least one selected term should match’: https://i.imgur.com/uHz3gjs.png
That means, that any of the choosen boxes matches, the result is not filtered out. It’s sort of an OR logic.
I hope this helps.