Can’t Filter variations on backorder

Hello, I am new to this plugin, and I have installed the latest version on my site.

I have a product that I want to filter. It’s called ‘Knot Ring’ and it has variations.

it has 2 sizes F and G, and it has 2 materials Silver and Gold Plated.

Variation F/Silver is out of stock but available on backorder.

However when I select the Silver attribute filter and the size F attribute filter and select the stock status ‘on backorder’ I can’t see my product. Does WBW Filter work for this type of variation filter on backorders? If so what are the configurations?

Kind regards, thanks for your help.

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