What could be a reason a user cannot see data in a report shared with them?

The reason that a user may not see data in a report shared with them is that they are not shared to any sheets from which the report is pulling data. In Smartsheet, reports aggregate information from various sheets. If a user does not have access to the original sheets that contain the data being pulled into the report, they will not be able to see that data, even though they have been granted access to the report itself. Access permissions are specific to both the reports and the sheets that feed data into them. Therefore, if the user lacks sharing permissions on the underlying sheets, they will encounter limitations in visibility regarding the data presented in the report.