You might be in a bit of a bind if you don't know what E-mail address you used to buy the
license. I'm going to assume you think it was one address from a choice of 2 or 3. I'm
hoping you know those addresses but just don't remember which one you used. In that
case, click this:
https://groups.google.com/g/video-downloadhelper-q-and-a/c/BzPLK2YyL-s
You'll probably want to bookmark that one for easy reference. I recommend you read that
entire thread, if not now, eventually. As you read through that you'll come across a
reference to what to do if you've lost your license. You can skip quickly to the
relevant reference by doing a string search on "lost" in there. That will reposition the
web page to the right reference. There is a link there that you should click. It will
take you to a page where you're supposed to enter your E-mail address. Try each of your
E-mail addresses in turn. Let's hope one of them gives you the response you're looking
for.
While you are reading through that other thread, you'll come across a reference to the
VDH license. This is more of a background discussion of the license & what it does. You
can skip quickly to that reference by doing a string search on "philosophy" in there.
Click this other link you'll see & read up on the license. I suspect there are some
ideas in there that will be useful to you.
Good luck!