You have missed the voltage on the negative end of the LED (The end that is connected to +V) There are three possible causes for the LED not being lit.
1 There is no voltage on the +V end of the LED
2 The LED is faulty
3 The led is connected the wrong way round.

Les.

Hi Les

The LED is in a speedo which has a 12v supply, all I have is a wire coming out of the unit to ground to operate the LED

The led works when I ground it

 

Hi Les

The LED is in a speedo which has a 12v supply, all I have is a wire coming out of the unit to ground to operate the LED

The led works when I ground it

Is the ground of your circuit connected to the same ground which lights the LED?

 

Is the ground of your circuit connected to the same ground which lights the LED?

Yes it is
Same ground...

 

Yes it is
Same ground...

I assume that the 600Ω resistor in series with the LED is part of your circuit not part of the speedo. Please confirm if this is so or not.

If you connect the wire from the speedo to the ground of your circuit does the LED light?

 

I assume that the 600Ω resistor in series with the LED is part of your circuit not part of the speedo. Please confirm if this is so or not.

If you connect the wire from the speedo to the ground of your circuit does the LED light?

Yes the 600ohm resistor is on the new circuit board.
Yes the led lights if grounded on new circuit board and also on the bikes ground..

 

I think we are only left with the possibly that the LED wire isn't connected to the resistor.
Can you please measure the voltage on the LED wire where it connects to your circuit and on both ends of the resistor.