Turn the wheel using your thumb and finger. Do not block the line of sight between the WallCast unit and the LED Sensor..
Turn the wheel until the number shown in the picture on this page is shown on the LED Sensor
Make sure there are no high protrusions on the board such as magnets stuck to the board, cards, post it notes etc. between the orange marker cross and the WallCast unit. If there are remove them. Note that nothing should be stuck to your board. Your board surface needs to be clean and free from items. See the Install Guide
If this does not solve your problem go to support.prometheanworld.com. A new LED Sensor or WallCast unit may be required.