If you've followed the guide then it should work but, just to double check:
Have you definitely burnt the disk from the extracted iso image correctly? There should be folders with files in on the cd/dvd if you have, if not their will just be the iso file.
When you go to put the cd in the RNS it should be switched off with car's ignition off, I.e. unlock the car, open the door and just offer up the cd to the RNS, it'll wake itself up and take the cd.
If this isn't working then perhaps you've been unlucky with your cd burning. Give it one last try with a different brand of disk using a different computer to burn it.