By switching on & off, I assume you mean in the browser settings in the extension
manager. On Firefox, it's what you get with Ctrl+Shift+a in the Extensions section. I
have disabled & enabled VDH there on a number of occasions & it has always come back on.
If you're not on Firefox, maybe it doesn't work so reliably. There is one thing you can
try, though. Click this link:
https://groups.google.com/g/video-downloadhelper-q-and-a/c/BzPLK2YyL-s
You'll probably want to bookmark that for easy reference. For this particular case, do a
string search on "reload the extension" in there. That will give you a link you should
click. Read what's there & try that. See if that doesn't get you going again. Do come
back & post whether that helped. Use the Reply all button to post here again. Do not
use the Reply to author button. Use Reply all.