My 6 month old GSD doesn't have any interest in biting a tug or a towel. As an 8 week old puppy he was very good at biting. Should I forget about doing Schutzhund?

I have a 6 months old GSD Working Line puppy, at 8 weeks he was very good biting, but now he doesn't have any interest on biting tugs, a towel or something else, I have been using the techniques on The Power of Training Dogs with Food and he is chasing the food very nice and no issues with the food, tones of food drive, what should I do differently? Should I forget about him been a Sch Dog as the protection work might be an issue? I watched a video from Michael Ellis saying that some dogs shouldn't be trained on Protection, but is not really clear to me the kind of dogs that shouldn't be trained. If my dogs seems not to be interested on biting things, is he the kind of dog that is not a good idea to train in protection? He is very social, outgoing, confident, no nerves issues, etc.

Thank you for your help Cindy!