Apologies if this is already covered somewhere. I have a recently installed Ultegra di2 group stop shifting on the front derailleur suddenly. rear shifts work fine and the front derailleur still autotrims, but it doesn't respond to the shifter at all. The battery is fully charged and it was working fine prior to the sudden onset. Is there an straightforward way to diagnose where (shifter, derailleur, wire, junction, ?) the problem is? I've done the standard obvious things you'd do for a computer (check the wire connections, unplug/replug the battery).
thanks for any help/suggestions,