Hi,
Thank you for all the details, I logged in and found a few configuration related issues, and corrected them.
– There was a content type filter active, that prevented search in content. You can re-create it if you need it, but for now I have removed them.
– None of the category filters were active, so everything was excluded. I have changed this option back to the default, then the filter is ignored until at least one category is selected.
– I have also changed the checkbox logic, I think it is better for your case.