Works perfectly if you set it up properly!

This was great. We are a publisher, so the inability to upload .epub files as a Woocommerce product was a killer. It uses the WordPress file types list.

What you have to do is remember to go to Settings in WordPress and select the file types you want AND scroll right to the bottom and save the changes. I didn’t do that first time – thinking that toggling the checkbox was enough, so it didn’t remember.