Shifter for the front derailleur is not longer working. On a ride, I was shifting up and it was sluggish moving up and eventually gave way. I thought the cable had snapped but on inspection, the cable seems fine, I think its a problem with the shifter. Its currently stuck in the small chainring. When trying to shift up to the big chain ring, the leaver moves around with a clicking sounds but the other half of the shifter (with the cable) doesn't move. It seems like the ratchet isn't engaging properly. I've taken it apart and can't see any obvious signs of wear. If it only takes a very small amount of wear for it to slip, that could be it though and I'm assuming I may need a new shifter. Obviously don't want to buy one if that's not the problem though.
Any other ideas?

Sram is pretty liberal with their warranties. Take it to a shop .