Can't get encoder outputs working with FIT0487 - they're open drain, right?

I am running an FIT0487 at 6V (motor is turning), and the Encoder at 3.3V (green LED is lighting up).

I assume that Encoder outputs are open drain, so have them pulled up to 3.3V with 10Kohm resistor.

But I'm not getting any pulses.  I've checked the wiring 3X.  Not sure what else to try.  Any suggestions?