In a webmaster hangout, Google’s John Mueller made clear that Google will treat your new domain as a totally new website if you cannot redirect your old domain to your new domain:
You can’t fix that, right. So from our point of view what would happen then is that we would probably drop the old domain and treat the new domain like a new site, like a separate site. That’s kind of the extreme situation, obviously you as someone who is running that business knows that area a bit and can probably get things sorted a lot faster than if you were really starting from scratch, but it is still a lot of work.”
You can view the video here: