You did nothing wrong but we've been migrating to a new server and here a problem occurred with the embeddable map. Sorry for the trouble - after all it's much faster now :-)
The problem with the map not showing is now fixed and your code will work again.
As a new and enthousiatic user I put on the 24the February a trainingmap on our website (www.htfc.nl). I choosed Embed GPS-Sport.net into your homepage, and than Trainingmap. However 3 days later the map wasn't displayed anymore. On the gps-sport website the generated code was: