In Looker Studio (formerly Data Studio), you might encounter a situation where applying a filter to your chart causes unique metrics to return null values.
If a unique metric is otherwise returning data correctly, applying a filter to the chart may cause it to return a null, No Data or NA value. In this case, the filter creates a situation where unique metric counts are attempted to be aggregated across non-unique dimensions.
For example, a unique "Reach" value may break from an attempt to filter non-unique values such as "Campaign name" or "Account name".
In some cases, adjusting the filter can fix the issue.
A common cause for the issue in the Facebook Ads data source is using a "Placement" filter to find Instagram- or Facebook-based data. To avoid the error, instead use the "Publisher platform" dimension to filter your data.
If you were filtering on a dimension such as "Campaign name", the issue might appear if multiple items are found with the filter. If you want to filter out 1 specific campaign, instead use a filter on a unique dimension such as the "Campaign ID" field.
In some cases, null values are intended behavior. For instance, filtering out some campaigns might turn their total reach value to null, if these reach values can’t be summed accurately. This is intended to avoid a false sum of unique values.