You need to tell us what sort of kit you have: most likely, you have no chlorine and need more. But some kits (DPD tablets) will read zero if the chlorine is zero, but will ALSO read zero if the chlorine is high!

You can get a cheap Walmart OTO kit (drops turn yellow) and test with it -- it's not super accurate, but it is super reliable, and will always give you some indication of what you've got (yellow = typical chlorine range; dark yellow to orange = high chlorine, to really high; brown = too high to swim.

Ben