The plug-in does not work automatically when you add a new download to a product. You have to go to “Products”->”MAK Download Permissions” and select the category and product you want to work on and either one or two files depending on the mode.
You also have direct links to the functions on WooCommerce product pages with downloadable files.
This allows you to have different policies for different products or even add some files to a product that you give past purchasers access to and other files where you don’t.
If at any time you have removed all files from a product and updated/saved it the plugin can not find any existing download files it can copy the permissions from and will be unable to copy download permissions for past orders of the product placed before all downloads were removed. In this case you can only add new permission.
You can not add download permissions for users who have not purchased the product which owns the files.