The campground "22,525 NORTH AMERICA CAMPGROUNDS (GPX) By Rivopom" come up as an invalid file when attempted to download on a Garmin GPS


What do you mean by "download on a Garmin GPS?"

I was able to download the file from The POI Factory to my computer.

I didn't try to install the file to a GPS with Garmin's POI Loader program. Is your failure stating "invalid file" coming from trying to load the file to your GPS with POI Loader which is the way to install the file?

Do not just copy the gpx file to your Garmin GPS or the over 22,525 data points will try to end up appearing as Favorites or Saved Places rather than Custom POIs and that's more Favorites than Garmin allows.

Let us know in more detail what you've tried and we'll figure it out.