2014 SLK 350. ECO mode worked fine since purchase Aug/2019. Realized last week that it hasn't engaged for a long time. Eco lite in dash bezel doesn't light up. Green "E" does show up on upper speedometer, so I am in ECO mode, but obviously the green ECO fails to light. I've read the list of all the conditions that have to be met for it to engage, and my car seems to have met all the criteria. I know some of you will say I should be thankful that it is not engaging, but I like my car to function as it was meant to. Is there a fuse in this system that I can check? Any other suggestions?