Hi a bit more info on your environment will help.
Check are you using data based on the format from another report suite then trying to match import it in a new report suite?
I think what you are missing is all matching s.props,events and or metrics. from the reference source report suite to the new one.
I'm not using a new report suite. I'm using the report suite that already acts as a "Global" roll-up to all the other report suites. Again, my company is already setup for the Device Co-op but do we need to create a brand new report suite for the People Metric?
When I look at roll ups 2 things..
When adding a report suite to an existing rollup, historical data is not included in the rollup.
Data contained in Rollup report suites does not support subrelations, segments, or any metrics that were introduced in marketing reports. Could this be the case with the People metric?
Since its available in child report suite and not Global one perhaps the project(I assume workspace) has an issue pulling in the data.
In project if you use child report suite does it work then?
Have you already talked with your account team and let them know it's not properly working? I would guess they would be more familiar with your implementation and report suite configuration, and would be able to provide more insight on what specifically needs to be done.
Another link worth checking out would be the People Metric help page.