First off, you should have this in your bookmarks:
https://groups.google.com/g/video-downloadhelper-q-and-a/c/BzPLK2YyL-s
Be sure you expand that so the full text of every post in the thread is visible. That is
a useful tool on general principles. You should read the whole thing, if not today in a
single sitting, bit by bit over time.
Specific to the topic at hand, look for (Find in Page) "VDH icon" on that web page. That
will give you a link to a tutorial on a possible solution. Maybe you've already found
that but I thought I'd give that one a boost in case you haven't.
If you have a shiny new computer with a shiny new Firefox, why are you running a shabby
old CoApp? You need to be running the latest VDH & the latest CoApp. Where do you find
those? Look at the home page of this forum. Really look at the page. Particularly at
the top, the part your eyes always skip over. Actually read it. That should get you to
the latest software. The latest VDH means the latest beta. The public release is
plagued with too many problems. Get the latest VDH beta. Also the latest 2.x CoApp.
There is also relevant help here:
https://groups.google.com/g/video-downloadhelper-q-and-a/c/jRjBH5lDctw
https://groups.google.com/g/video-downloadhelper-q-and-a/c/guxm6mUhm8s
Those discussions mention specific versions that are already out of date. Get the newer
versions. But other than those numbers, all the advice there is still applicable.