How do you make all your custom RTC attributes show up in Report Builder 6.0.3?

We have a project area where we have added several custom attributes to various work items in RTC 6.0.3. Some of these custom attributes are showing up as selectable attributes in Report Builder, but we have 2 attributes that are not. They are of type Deliverable and Iteration. Is there anything I can do to have these attributes show up for this project? Other standard fields of Deliverable and Iteration type are available.
Accepted answer

Hi Jamie,
There is a similar question in the past.
https://jazz.net/forum/questions/232315/custom-attribute-of-type-deliverable-is-not-accessible-in-report-builder-jazz-reporting-service
https://jazz.net/forum/questions/216859/what-custom-rtc-fields-are-available-in-the-data-warehouse
I suppose all Deliverable type custom attributes are unavailable in JRS, but Iteration should be available in REQUEST_ITERATION_EXT. Does this custom attribute have a value in at least one workitem, and refresh the data source?