The red lead of the PR180 should be connected to the LINE and the black lead connected to traveler A. The connections do not change based on the sensor being on the line side so you can still follow the wiring diagram on the instruction sheet.
To verify if your device is wired correctly, when the sensor is in the AUTO position you should be able to turn the lights on from the 3-way switch if the lights are currently off. Once switched on from the 3-way switch the sensor will shut the lights off once occupancy is no longer detected. You will not be able to shut the lights off at all from the 3-way switch no matter what position the sensor is in.