My jewelry factory isn't working either. I'm betting it's a bug.
The factory has been built for six or seven years now, and each year its output level fluctuates between about 1 and 6. It has all the improvements except the fine jewelry one, with housing and a (third, half-full) teamster office right across the street. The factory's income level is 0 for both current year and lifetime, and the net profit (lifetime) is -48,000.
Argh! Please fix this or else explain what I'm doing wrong. I sure can't see what it is.