Your SCS will be tight on the fork, it's meant to be. Just open the SCS up a tad by either lightly tapping a chisel/screw driver into the slit a little or doing the coin trick as it's comonly known.
theres no way your fork can be "defective" thats impossible, your forktube might be bent, but scs are suppose to fit tight on forks, just have someone that actually knows how to work a scs do it for you
haha a bike shop told you that, i dont trust them but thankfully i know better. all threadless forks are tiny bit bigger because its not easy getting the right tubing for them. but yeah as stuckwon-do said, stretch the clamp so it comes out and then get back to us.