Aftermarket electric fan wiring and switch not working

I asked around and installed an electric fan with wiring because my old factory fan broke. The fan had one blue and one black 16G braided wire coming directly from the fan. I attached the black (ground) to a bolt on the frame. I routed the blue to the switch and to a fuze to the positve side of the battery. I used a braided 12G 20 amp fuze assembly and switch. I used wire nuts and electrical tape to cover the splicing. I used braided 16G blue and black wire to attach the existing blue and black fan wires. The fan never turned on via the switch when I turned the key to the on position or when I started the vehicle. I tried switching the two blue wires to oppposite sides of the switch and still nothing. What could I be doing wrong? How could I do it all better? Any answers?