The light on the DAQ unit is NOT a power lamp. It is an indicator of data transmission. The light goes on and off depending on the ready state of the unit. If the usb bus is active, if it is ready to sample or in the process of sampling the light will be on. The light may go off after a period of inactivity. If the light is off and you open MillMax, select a tool type and the initialization begins, the light will come on. If it does not, then you may have a defective USB port on your computer. Try another USB port to see if it works there.