PL-08N inductive sensor not turning off
Figure 1. An NPN proximity switch.

The diagram on the front of the PL-08N (1) switch in your question indicates that the load (3) should be connected between supply positive (2, brown) and output (black). Internally it is using an NPN (or equivalent) transistor to do the switching. These are often referred to as NPN or "current sinking" type sensors.