Why are all my scores from the AI Preview and Rank zero?

The AI Preview and Rank requires all references to have at least a title configured for them. If there are references that have blank (empty) titles, then the Preview and Rank functionality will be unable to properly determine a score for the references and will default the scores to all zeroes (0).  

To remedy this situation, run a report in Datarama, displaying the "Title" reference field (found on the Reference Display Options tab) and search for the references with blank titles. Update these references to include a title on the Edit References screen (References > Edit References). Once complete, rerun the AI Preview and Rank and the appropriate scores will be calculated.