front gear shifters not working
From the question I'll assume the shifter lever moves, but it does not pull the cable.

My guess is that the shifter end of the cable is not seated in the shifter properly, or has become hung up somewhere. This may have happened when the cable was loose while not connected to the derailleur.


Unclamp the cable from the derailleur
Find where the cable is seated in the shifter, you'll have to pull back the rubber hood covers to find this, check the boss on the end of the cable is actually seated in the shifter properly 
Check the cable run: verify the cable runs the housing unimpeded, especially at the shifter end, make sure housings are fitted in bosses properly, look for snags in the cable
To test, hold the cable where it run exposed or at the derailleur and put a little tension on it, actuate the shift levers and feel for the cable moving