SSRS report - some users see data, others don't

I have an SSRS report that data shows on the report for some users but doesn't show for other users. All users can run the report. I have been looking at SSRS security but the access looks the same for all users. Any help would be greatly appreciated.

What is the source for the report? A query or stored proc? If possible, you might see if people from both groups can run the query/proc and get the same or different results.