First thing that you need to do in order for Task Board Scanner to work is to instruct Agile Cards plugin what is your physical task board layout. Go to Agile Cards: Define Task Board Layout in your project menu and select columns which our task board consists of.
After defining the columns you need to print so called splitters, that are to be sticked between task board column areas, so that Agile Cards plugin will be able to automatically separate these areas on a photo. Press Print splitters button to generate splitters. Please remember that regions on your task board should be vertically-splitted.