how to run the sample program :markers

[nlp1988]

I have set two trackables,but can't get the TT_TrackableLocation of them. The output is :
Frame #100:
Frame #200:
Frame #300:
Frame #400:
...

how to solve this problem. Is there any setting we should do in the software Tracking Tools?
Thank you!

[NaturalPoint - Mike]

Do you have a calibration file loaded?

Can you use TT_CameraMarkerCount to see if you're seeing 2d markers on any individual cameras?