Remove any obstructions from the pen tray’s infrared light sensors. Moisten a cotton swab with a household glass cleaner and carefully wipe the sensors. Also, you can spray compressed air over the sensors to remove debris.
If the lights remain lit after you’ve cleaned the sensors, see SMART Board 600 Series Interactive Whiteboards May Not Correctly Detect Pen Tray Tools to determine if your pen tray’s sensors are working, because you may require a replacement tray. Contact your local reseller or SMART Support or further assistance.