I've found mine doesn't always engage, sometimes if I coast to a junction and apply the brakes softly over a large distance- it says somewhere there needs to enough braking pressure for it to work. I'm not sure if that is the reason though.
Is your ECO button lit up? I think that is something to do with it too.
I know someone with an Alfa, who says hers doesn't always work too
Edited by: gillsid