The Peugeot was doing that - would NOT shift into 1st or 2nd gear no matter what I did, but according to my maintainence book (I bought the Bicycling Mag Bike Maintainence for all types of bikes coz the pictures are Real photos) it was just a matter of adjusting the high/low screws on the back derailleur. If yours is the front, there should be 2 screws on the mount by the front maybe (maybe not) marked H n L. One of them controls the throw down and the other - OK...I'm NOT going to say it....the throw up! (oops...yes I did). I'm guessing that your bike shop guys have played with that, but I guessed my bike shop guys had done the same thing on the Peugeot. All I know is, I played with it myself, and fixed the problem.
Hope this helps.
Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body, but rather to skid in sideways, champagne in one hand, strawberries in the other, body thoroughly used up, totally worn out and screaming: "Yeah Baby! What a Ride!"