How to load labels in a Zebra ZD220d

Zebra's ZD220d printers can use 3 different types of media: continuous, marked media, and labels.
As such there are 2 different sensors: one for gaps/continuous (transmissive sensor) and another for black marks/notches (reflective sensor).
The reflective sensor is movable, so check this is positioned in the correct place to determine the media mark/identifier.