I’m very sorry you had a problem with this plugin author’s pro version but these forums are not for airing your commercial dispute.
For pro or commercial product support please contact the author directly on their site.
https://www.wpdownloadmanager.com/
Commercial products are not supported in these forums. As you are their customer I am sure they will have no problem supporting you there.
Note to @codename065 I had to look at your plugin’s source code to find that link and I can’t find any contact page on your site. I have have missed it but it sure isn’t apparent.
You may want to add such a link to your plugin page here.
How you reply to unhappy customer here is important too but please refrain from getting into it with this user. If you can provide a means for the user to take it to your site (a contact URL would be really good) then I’ll close this review.