Every time we compile our code from Eclipse while connected to a RoboRio, it says “Build Successful.” But when we open up the Driver Station to Enable the code, it gives us a warning that we don’t have robot code. 
You’re probably erroring out. You can check this by hitting the gear above the ds console and clicking “prints” than redeploying code
If there is no error message just reboot the roboRIO. Sometimes the robot code does not start even though the code should run fine. I found this when I made one minor change (hardly code breaking) and the code did not start or provide an error message.