The pickups are composed of two small magnets which sense a small metal plate which spins past the sensors.

First check your opto + rest of circuit by providing stimulus with a battery (or some other source) to see if the circuitry is working fine.

If your circuit is working, then I doubt that your opto couplers (when connected to pick up) are not getting forward biased. Can you check it?

In any case, a current limiting resistor is a must in series with the LED of the opto.