Put an earth on tag 7 of the instrument panel should light the lamp (be careful,there is a battery on tag 5.) If this lights the lamp then your missing the earth from the neutral switch.
Try putting an earth wire on the neutral switch connection, if it lights then switch is faulty. (unlikely if you have changed the switch)
An earth goes from the neutral switch to the bulb. Does the bike start without having to pull in the clutch (with bike out of gear)?
The diagram is not too helpful. It shows 2 wires going from the switch, one to the lamp and one to the starter relay, does not show where they split. If the bike does not start without the clutch pulled in then the wire is suspect up to the point where they split (1 to starter relay, 1 to the lamp). If it does start without the clutch then the wire is suspect after the split and up to the lamp.
I have found the wiring was different on this part of the circuit, on my 2005 GSA. you may well find the fault in the joins that are crimped along the RHS of the headstock, its the stub ended bit of the harness.