You are missing the "knob" that adjusts the height, that "3 leaf clover" might be the remains of it.
The plastic bit with the circle marks sits inside the knob and is just a useless height indicator.
Because you have no adjustment knob the machine will be at it's lowest setting.
Try to source a knob or maybe try a dirty big nut on the thread instead as you screw clockwise it will lift the height.
The following page has a photo of the mower and missing knob
https://www.outdoorking.com.au/forum/ubbthreads.php?ubb=showflat&Number=35649
