The most prevalent answer to this is that the microlight is still in factory setting. You may have recently bought the light or replaced the batteries and restoring it to standard function can be done by holding down the button for 15 seconds.

The Inova microlight is designed to turn off after four minutes of usage when it is on the high setting. This is not a defect, but a function to conserve battery life. Just simply click it back on if you need to continue using the light, or use the second or third mode as they wont turn off after four minutes.