What does it mean when a NetGalley reviewer responds, "Not eligible for review yet; will post when Amazon allows"?

If your book is in preorder, NetGalley reviewers can’t post reader reviews yet. Once your book is officially released on your launch date, NetGalley reviewers can begin posting. The best time to email your NetGalley reviewers is on your book's launch day. Make sure to include a link to your book’s product page when you ask them to post their review.