This is a very frustrating problem.
Whenever I upload my Garmin running data, I use Garmin Express. It launches my default browser, Firefox for Macintosh (OSX 10.9.4), and the modern page (dark blue background, with white menu and buttons in upper left corner). None of the buttons work, so I cannot log in.
Then I remember to switch to Safari, which is book-marked to the old classic Garmin Connect login page (white background, with login fields in the center of page). I log in using the classic interface. This works and launches the modern page (dark blue background), but this time all the modern buttons do work and I can see the data I uploaded.
Why won't any of the buttons work with Firefox for Mac?