Hi,
I would suggest that you power the Sensor with 8V as shown in your circuit, do not connect the White and Red leads.
You should be able to measure 4V on the RED wire to 0Volts, also measure 4V on the WHITE wire.
Measuring , using a sensitive voltmeter, between RED and WHITE it should be very close to 0V, then load the sensor and the WHITE wire should go a few milliVolts positive with respect to the RED wire.
The above test should check the Sensor, tell me what the voltage measurements indicate.