I've never used an Edge so I'll leave any device-related advice to someone else, but -
when using a GPX file which is basically of unknown origin (whether provided by an organiser, or a friend, or just 'found' by searching the internet - you shouldn't assume that it is going to just work and do what you want. The file may have been designed to work in one particular model of GPS and not be optimal for your model - or worse, for example the org may have been given that file by someone else who rode the event the year before, and who is a total dingbat - you just don't know. So you need to check it somehow, maybe by uploading it to a planner site such as BikeHike, checking the points count and checking it goes where you expect, and doesn't cut off half way round, then re-downloading it in a format you know works (planners often give a good choice of export formats).
x-post with vorsprung