Hey!
I had the same problem. The shifter was working intermittently and quite often not shifting at all; turns out many 4700 left shifter have this problem according to people on the internet. After trying to make it work for some time, ultimately my solution was replacing it...
My road fixed in progress (Dodici Veloce). Thanks @gaston for the wheelset ! Obviously, a proper crankset is de rigueur when I have some money to spend.
I did, when it was set up too high.