Saving Hawaii

Have you tried to add them manually? Works easily for me. Go to the spot on the National Bike Challenge page where you log your miles, click "log miles". At the top right of the pop-up you'll see two options. Both give you a calendar thing. Then go back to the day you rode on, click on it, and then add your miles in. I can see why people would prefer to let Endomondo or whatever do that for them, but it's not hard to do it by hand.