ANALOUEI

I have 2013 a RX450h. The blue fading light in the dashboard used to work with acceleration. It would come on when the rev counter was in Blue ECO area and would go out when the rev counter was in acceleration are. It has been a while that this does not happen. I know the light bulb is not broken because the light comes on when i enter the car and then it goes out. there is no reference to this in the manual. Any idea how i can set this function? thanks