Sometimes customers are experiencing the problem of missing billing statistics because of daemon, delayed jobs, cron, raw statistics temporary failures. After the mentioned services get started, raw statistics data gets inserted into the DB and afterwards aggregated into raw hourly statistics (in most of cases). Having raw hourly stats in DB allows generating billing statistics based on it. That doesn't happen automatically because of peculiarities of billing statistics generation. However, it can be done manually running the rake task specifying the period (billing:calculate_hourly_stats_for_missed_period [:start_time, :end_time]).
RAILS_ENV=production rake billing:calculate_hourly_stats_for_missed_period\['2014-06-01 01:00:00','2014-06-05 23:00:00'\]