what is gatsbys response to nicks assertion that he cannot repeat the past?

Gatsby's response to Nick's observation that you can't repeat the past is incredulity. He says, "Can't repeat the past? Why of course you can!" To him, it seems perfectly reasonable to expect that Daisy would be able to tell Tom that she never loved him, and pick up where she left off with him, Gatsby, five years ago. Gatsby is determined to "fix everything just the way it was before". As he talks, Nick understands that in actuality, Gatsby wants to recover more than just Daisy. He is looking for "something, some idea of himself perhaps, that had gone into loving Daisy". His life has been incomplete since he lost her, and he somehow feels that if he could just go back and do it all again the right way, he would find the thing that he has been missing (Chapter VI).

Gatsby ignores what Nick says, preferring not to have an argument with his friend.