Explanation for why traits and segments might not show up in the Overlap Reports page.
Why don't users see certain traits and segments listed in the overlap reports page when attempting to run an overlap report?
A minimum unique visitor requirement needs to be met in order for a trait or segment to be listed in the overlap reports.
For Traits: 28000 over 14-day period
For Segments: 70000 real-time users over 14-day period
More details about this can be found at this URL: