Have you disabled my plugin? After sharing it just shows the add to cart.
Brief help though, maybe it will give you some clues. If a download simply redirects back to the product page, this can happen because the download checks didn’t return valid. These are mostly the same checks that occur to determine whether the download button appears on the product page. For example if the price check didn’t return free during download, it will fail. I’ve seen this before when plugins changed the price dynamically during page load, like membership price plugins, and I had to build in support for them.
The download checks might not match the frontend display check because not all your plugins are loaded in the backend during the download procedure. Either way it’s a difficult issue to debug.
If you want to try and get my plugin working I recommend loading up a new blank site with a default theme (Storefront is a good one as it’s built for WooCommerce), and just install WooCommerce and Free Downloads WooCommerce. Create a simple downloadable virtual product with 0.00 price, add a file to download, and then everything should work. From there add your plugins/custom theme and see at what point it breaks. If it’s something I can replicate on my end I might be able to build in a fix for it.