Dashboards: Indicator Distinct Feature Displaying No Data

[KatieHaffie]

Hi, I've created a dashboard with a indicator element. I'm trying to use the distinct feature to return a count of the number of unique users within a data set. Whenever I use the distinct option, the error no data appears on the indicator. 

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The data for the dashboard is from a related table within a feature layer. Can anyone think of a solution?