If the display function does not work, replace the meter unit.

Check 3-6: Neutral Indicator Light (LED) Inspection
Meter Unit Circuit (ZX1000J Model)Liquid Gasket, Non-permanent Locking Agent
For applications that require Liquid Gasket or a
Non-permanent Locking Agent, clean the surfaces so
that no oil residue remains before applying liquid gasket or
non-permanent locking agent. Do not apply them excessively.
Excessive application can clog oil passages and
cause serious damage.
...
Electrical Leads
A two-color lead is identified first by the primary color and
then the stripe color. Unless instructed otherwise, electrical
leads must be connected to those of the same color.
Instrument
Use a meter that has enough accuracy for an accurate
measurement. Read the manufacture’s instructions ...
Rear Wheel Removal
Raise the rear wheel off the ground with the stand [A].
Remove:
Cotter Pin [A]
Rear Axle Nut [B]
Washer [C]
Rear Axle [D] (from Right Side)
Remove the rear wheel rotation sensor from the caliper
bracket (see Rear Wheel Rotation Sensor Removal in the
Brakes chapter).
...