Rear lights not working

Hello guys just need some help the rear main lights on my gti aren't working, indicators, reverse, fogs, and brake are all working even the front lights are working but the rear main lights and number plate lights aren't working in have cleaned the earth bar in the boot but still nothing is there a coloured wire I could trace or and thing in could try all suggestions welcome as will be trying everything, thanks 

Tail lights Burn out, have you checked that the Bulb is good and the Socket is clean and not corroded?

Same for the number plates, and have you checked the fuses for the rear tail lights and License lamps?

Hello just stopped in a indoor car park and switched lights on I realised the rear lights, dash light come on when the switch is pressed, so wondering if it the main switch, but I still can't get the number plate lights to work I have installed brand new number plate lights to, so just wondering if it could be wiring, does anyone know what wires are for number plate lights I know one light connects to the other so was wondering weather it's the wiring if I could trace it back to fuse board or switch i could see if it's a break a colour of the wire that goes to the number plate lights will be ideal many thanks 

Do you have a multimeter or a test lamp? It would help if you could see if you have voltage at the lamps by connecting one lead of the tester to the positive feed to the lamp and the other lead to a good earth connection (not the earth that the lights use). If you have 12v then it's the earth that's bad. You can then trace it to it's earthing point on the car and give it a good clean up. If you don't then it's a break in the cable, bad connection or fuse blown. Either way you'll have to follow the wires and check for voltage at every connection you come across until you find it. That said, it could well be corrosion on the lamp holders themselves. Good luck.

The number plate lamps are new ones so should be ok, I will have a look at the earth to them the main rear lights I believe it to be a switch as when pressing the switch to the on position and holding it they work but letting go the lights play up so i think that might be switch or something lose inside the switch, but the Number plate ones are bit weird lol of worst come to worst would it be ok to pinch a connection of the main rear lights so they come on with the rear light ideally I would like to get to the bottom of why they don't work lol