The app is not reacting to the IR pen
Make sure that the application you choose is designed to work with an IR light pen. The application icon shall be marked with the word PENS.
Check if the IR pen is in working order, i.e. it lights up after pressing the pen tip or pen button. If it is off, replace its batteries and check that it is on again. Press the IR pen down on the elements on the board or move on the IR pen across the floor. The app elements still are not responding? Go to step 3.
Limit sunlight to the projection area. The sun's rays that fall directly on the board can interfere with the pen light. If there is still a problem, go to step 4.
Enable automatic camera calibration. You can find it in Player
Settings > Advanced > Auto camera calibration. Follow the on-screen instructions. Launch the pen-controlled application and check its reaction to the pen light. If the problem still exists, go to step 5.
Make sure the LEDs on your device are NOT red when a pen-controlled app is running. The LEDs are located in the lower part of the housing, behind the tinted glass. If they are on, turn off the device. Then, turn it on again. Launch the pen-controlled app and check the LEDs. If the LEDs are on, contact a service technician.
See also the help card - How to use an interactive pen?.