There is a possibility that they put the clutch on backwards, as difficult as that is, also you may just have air in the lines. I would bleed the slave cylinder first, and of course make sure that you did not use cheap tranny fluid. Are you getting any clutch pedal tension? When I installed my clutch I was stumped, because I couldnt put it in gear. Come to find out the fluid just needed to warm up. Definately take it back. Good luck.