What's wrong with nail polish that doesn't dry?

I bought a bottle of nail polish in a lovely shade of green. The problem is, it does not dry. No joke. I've done everything- from sticking my fingers in ice-cold water to using the quick dry spray- it refuses to dry. 14 hours (no exaggeration) after applying the nail polish, it's still not completely dry. What's wrong with it?What's wrong with nail polish that doesn't dry?
I think it usually means it's too old or you possibly put it on too thick. I would either return it, or try putting some nail polish remover in the bottle to thin it down; then reapply. What's wrong with nail polish that doesn't dry?
either it's too old, you put it on too thick, if it's a frost, those always take forever to dry, or it's just a cheap brand.
may not be applied thinly enough. I apply 2-3 thin coats of color over a base coat. Also, helps a lot to use a quick dry top coat.