Facebook has recently made platform policy changes as referenced in the following Facebook developer blog post. As a result of these policy changes, Garmin has temporarily disabled the LiveTrack share via Facebook feature. As an alternative, users seeking to share a LiveTrack may continue to do so via email, or Twitter. We will continue to evaluate these requirements and the best options moving forward.
Use a browser on a tablet, then you have the option to export to FB, Twitter, E-mail and more. The option is hidden by a css class called "addthis_toolbox" (only helpful if you know something about css and html)