As typical with Asian made devices, often the GND is absent or not obvious if there is a GND symbol you should supply a ground conductor also the frame of the motor should be earth grounded.
The terminal marked GND on the terminal strip is probably just for the internal LV supply common, if so it is not the main ground of the unit.
Essentially the only thing in these VFD that need earth grounding is the power semiconductor large heat sink, the other is for any suppression device in the main power circuit.
Al.