This issue is not reproducible in ArcGIS Dashboards when the dataset is configured properly. Some values in the field configured with the category selector have extra spaces after the attribute value, while others do not. The selector then filters for only one of those values. Removing the extra spaces and reconfiguring the category selector resolves the issue. If the issue occurs for datasets where all values match, please contact Esri Support Services as additional information is required for further investigation.