The software reports that a LED failure is detected. Please disconnect the device by pressing the X in the upper right corner of the device window. Turn of the control unit and inspect the LED cable at the back entrance of the control unit. In case you have a single LED, please inspect the cable connected to the LED. If everything looks to be fine, power on the control unit, reconnect the device in the software and try to press FLIM. If the failure persists, please contact Lambert Instruments.