At the front derailleur (FD), undo the bolt which clamps the cable. If the FD cage can then be moved easily from side to side, the problem is in the lever/brifter. In my case, when I loosened the clamp bolt, I was able to move the levers. I guess my cable was a bit too tight in the first place.
If this fixes your problem, turn the barrel adjuster on the FD cable on the down tube fully clockwise and then unscrew it half a turn; put the chain onto the smallest chain ring (front) and pull the cable tightly through the cable clamp and tighten the bolt. Try changing gear with the FD. It should change smoothly across all chainrings. If not, turn the barrel adjuster a quarter turn anticlockwise to tighten the cable. Repeat until you are happy with the gear changes. Fine tune while riding. If you run out of adjustment on the barrel adjuster, you will have to pull the cable tighter at the FD and reclamp it. Hope this helps.