FAQ: The book is not released yet so I can't review
That's perfectly fine! Booksprout will send you an email when the book is live and ready for you to review.
In some cases, the author may have already published it on external websites such as Amazon, but they haven't yet told Booksprout where to find it. Until they do, you won't be able to complete your review. Not to worry though, nothing bad will happen to your account because of this.
The book is already published
If the author has already published the book but has not yet provided Booksprout with the link(s) to it on external websites such as Amazon, you may wish to contact them to kindly ask that they update their book within Booksprout. Once they add the links to those external websites you'll be able to complete your ARC review.