“Connection is either null or invalid” Error Only for HR Specialist (Custom Role)

Summary:

We have a BI Publisher report in the Custom folder. When I run the report using my implementation user, it works correctly and generates output. But when we log in as HR Specialist (custom role), we get the error:

Connection is either null or invalid

We have already assigned the custom HR Specialist role to both:

• The Report folder, and
• The Data Model folder

The same HR Specialist user can run other reports successfully, including reports that use tables like PER_ALL_PEOPLE_F. So the issue is only with this one BI Report / Data Model.

To debug the issue, I created a