Not possible to tell for sure what's wrong - too many variables. Spokes could be too short, you could be crossing more spokes than you think (can be easy to miss the 1st cross) or you could be lacing to the wrong holes. The first step is to take the parts back to the shop or call them to recheck the spoke length. You can also measure the spokes yourself, and can even determine the correct length on your own if you want to take the time to learn how. Google Sheldon build wheel - everything you need is there, from how to measure a spoke to spoke calculator links and wheel lacing instructions.