Let's start by looking over here:
https://groups.google.com/g/video-downloadhelper-q-and-a/c/BzPLK2YyL-s
There are many useful links in there, some of them relevant to this particular problem,
but you'll probably find others useful over time. Let's start by doing a string search
on "problem report" in there. You'll find 2 links there. You should click them both,
read up on how to post a proper problem report, then follow that advice. It's usually
important to know the specifics of your system environment. You mention Linux in your
thread title. You should also do a string search on "linux" in that Table of Contents
thread. You'll find several references to discussions of installing VDH & the CoApp on
Linux that will likely be helpful.
Good luck with your reading.