I tried some things with the “Search Anything” plugin and will describe my foundings below.
The search plugin returns 0 results when you hit the search button without typing any search terms. This also happens when you disable our plugin. I believe this is a bug in the search everything plugin. It even gives some SQL errors when I hit the search button without any search terms.
When I activate our plugin and go to the search page, I see all records. As soon as I filter on any field/column and hit the filter button (or search, they both do the same), I’ll get no results. The reason for this is because the search field is also posted in this request as empty ( ?s= ). This results in the same behavior as described above.
Now I filter on a custom field column on the value ‘stefan’ (which should return a result) and also put in the search term ‘stefan’ in the search box and hit Search/filter. Now I have one post that contains ‘stefan’ in my post. This means both plugins do work together as long as there is a search term provided.
But keep in mind that both filtering and search work together as an ‘AND’ operator. This means that only records with filter value ‘X’ and search value ‘Y’ in the same posts are found.
Are you sure you use the search feature to narrow down the results that are already filtered by our selection? Could you also have a look if you have sorting active on any column? Look for the ‘reset sorting’ button on top of your screen and hit it and try again. By default when sorting is active, records with no value are not shown in the overview.
Now about a possible solution. I believe the only problem here is the empty s param in the URL. You could write a redirect and remove the empty ‘s’ param from the URL if this param is empty. Of course, better would be that the search everything plugin does nothing when the search param is empty. You could write a bug report for this on their support forum. Other than this, there is not much we can do on our side to help you further with this problem.