Here is the code for SCALEBAR in the mapfile:
SCALEBAR
IMAGECOLOR 255 255 255
LABEL
COLOR 0 0 0
SIZE SMALL
END
STYLE 1
SIZE 100 2
COLOR 0 0 0
UNITS MILES
INTERVALS 2
TRANSPARENT FALSE
STATUS ON
END
No glaring/noticeable errors in /tmp/mapserver3.log. What would the issue be?
EDIT1: had to change status from ON to EMBED.