If the report is based on billing templates then along with having project manager permission he will also require billing manager permissions in his profile to view the data. Kindly let me know on what template is the report based? to find out click on Settings in that report and you can find the template on the top right hand corner.
To assign additional permissions to a users profile:-
1. Log into Replicon as Administrator. 2. Go to Users. 3. Edit the users profile. 4. Go to Roles & Permissions. 5. Assign Billing Manager permissions. 6. Save the settings.