Airnav only created certain planes and colourshcemes as 3D models. I don't think they currently have plans to do any more, which in my opinion is not a positive thing. Another shiny new toy given to users and not supported by Airnav from the moment it is created.
Also not all the models are against the correct codes like the A388 models are stored against the incorrect A380 and all B77W models are against B773.
They did this because their own bug corrupted the ICAO codes and instead of fixing the bug, they created the models to the match the bug - go figure.
Those corrupted codes of course now do not now appear on the records that are in the new updated Navdata file created from our updating work. Therefore any A388 or B77W you see will not have a model even though they exist in a corrupted form. Therefore Airnav have shot themselves in the foot.
To see which of the few models and colourschemes actually have been created against the correct ICAO codes, look in your C:/Airnav folder and review the files in the GE Models folder. Anything that is not there will appear as a blob.