I just got my TV to recognize an AV (composite) input, and when I turned on my N64, it worked. Sadly, what I did does not make much sense to me, but here it is, just in case it'll help you.
Up 'till today, in the input list only component and not composite (AV) would be available. I disconnected and connected my TV (this was unintended) and then, with the TV turned off, I disconnected the component adapter my TV came with. With it disconnected from the TV, I connected into it the cables from my N64, and then I connected the adapter to the TV. I turned on the TV and this time AV (composite) was in the input list, and component wasn't.
I think you don't have an adapter like I do but a direct component port, but I hope this will help you somehow. Good luck!