You can send workouts and courses from the individual menus in Connect or add them to the Calendar then send to the device from the Calendar page. If you have having trouble sending more then one item at a time, I suggest you remove everything from the Sync menu in Connect then send the items individually from their menus. You might come across one workout or course that will not transfer. Delete it then recreate it and try again.
Curt, I am able to get courses from connect to the express. They get recognized as something that needs to be synced. Then I hit sync now. After that I get a message stating "Sorry, we could not sync your device. Please try again." With a hyperlink to the possible errors to the ANT stick.
I am sorry that you are having trouble with Garmin Express. First, lets just try some basic troubleshooting. Please make sure that Garmin Express is up to date by following the instructions here:
How do I update Garmin Express?
Next, remove the Forerunner 310xt from Garmin Express, restart the computer and then repair the device. To remove the device from Garmin Express, see the FAQ below and choose the option to remove the device from Garmin Connect when prompted:
How do I delete a fitness device from Garmin Express?
If these steps do not solve the problem, there may be some corruption to the folder on the device that the workouts are stored in. A master reset will most likely solve this problem. Please follow the instruction in the FAQ below to reset the device:
How do I reset my Forerunner 910XT and 310XT?
