Hi Chuck
I have been going round in circles with this this morning, including trying and failing to install a copy of your site locally so I could continue testing without disturbing you.
In the end I started to create a new View for testing (called "Toolset", inserted on the page of the same name), which includes just a couple of filters and simply lists the matching posts.
This does work correctly.
Which led me back to the "Single Product List Entry" View which does not.
And the explanation for why the filters are not working turns out to be fairly simple (although accounting for how we ended up in this situation may not be).
When it comes to adding filters to a View it is helpful to think of them in terms of front-end filters and back-end filters.
By back-end filters I mean filters that you add to the Query Filter section of a View, which apply every time the View is loaded, wherever and whenever it is loaded. Such a filter might be a post author filter, for example, where the post author should be the current user, so that whenever someone sees this View on the front end they will only see their own posts.
Front-end filters are the search form filters you have been adding in the search and pagination section, where users can use the front-end filter controls to modify the results of the View.
Now, when you create a new View and specify that this will be a custom search View, the Query Filter section is normally hidden. You can expose it by using the Screen Options tab at the very top of the page and checking the Query Filter checkbox.
Now, when adding a front end filter using the New Filter button, hidden from sight, Views quietly adds a Query Filter for that filter control which specifies that it is listening to the relevant URL parameter for the filter value.
Because the Query Filter section is normally hidden you don't notice that, but if you expose the Query Filter section and use the New Filter button to add filter controls, you'll see that a new Query Filter is added each time.
But look at the Query Filter section for your Single Product List Entry View. It is empty. You have front-end filter controls, but they don't do anything, because there are no Query Filters listening to the URL parameters added by these filter controls.
I don't know how you ended up in this position, but the best way to fix it is to delete the filter controls from the Search and Pagination section, and then use the New Filter button to add them back, one by one, checking that a corresponding filter is being added to the Query Filter section.
Try that, and when you see that it is working, you can activate the code snippet that will prevent any results being shown until something has been searched for.