did you reclamp the cable? – if cable is too tight irrespective of limit settings won’t drop to granny
I’d also try turning the mech slightly but chain rub is a danger
depends a bit on the front mech – just did a quick google and Shimano generally warn against it though I’m surprised doesn’t work at all
“For Installation to the Bicycle, and Maintenance:
• A triple front derailleur cannot be used for a double crankset because the shifting points do not match. A double front
derailleur cannot also be used for a triple crankset.
Double: FD-M675, M676, 3500, A070
Triple: FD-M670, M671, T670, T671, 3503″
from http://si.shimano.com/php/download.php?file=pdf/dm/DM-FD0001-00-ENG.pdf
sure a pro’ fettler will be along shortly but a bump