I figured it out and thought I would post to help others...
if you are going to use a route for NAVIGATION, you need to download the gpx TRACK file, not the gpx route file.
I have downloaded my first route so I can use it on my Suunto9 watch.
Multiple programs say it is "corrupt or not a supported file type" (Suunto app, gpx viewer, movescount.com)
DESKTOP TABLET MOBILE
(no app download required)