It lights up green, but I can’t turn it off by pressing it. A work-around I find is to use the S/E mode button instead, which turns off the ECO Auto Stop/Start light.

Any other cars with the same behavior? thanks!

 

Check auxiliary battery.

 

The auxiliary battery is brand new. Actually the Auto Stop/Start function itself works! It’s just the ECO “A”button doesn’t work. Maybe a blown fuse?