The first thing to check when your report shows no data, or if records are missing from your report is whether or not that report is being filtered. Sometimes a filter added by yourself or a colleague might not have been removed after an earlier session. You can tell if a report is being filtered by the (Report Filtered) label next to the report's name.
Try removing any filters by clicking [Edit Report] instead of [Show Report] on the previous page. For more on managing filters see, Filtering your reports
If after removing any filters you still think there is data missing contact support. Be sure to include which report you're running, the date range, and an example of a record that is missing.