Check that--the SD just connected to the robot. the Connection indicator is green now. I used a code I found (and modified slightly) from a 2011 thread on the SmartDashboard.
Code:
double value = 42.85
SmartDashboard::init();
SmartDashboard:PutNumber("Stuff!", value)
I guess the code, not the SmartDashboard itself, was the issue. Huh. I ws sure we checked it before uploading...ah well. Live and learn. Thanks to everyone who offered their advice!