Why do I sometimes see the error No data available when performing a drill-in in a Explore report?
By default, drill-in does not work on any custom attribute value of null, so if you’re drilling in on a null value (or a combination of values including at least one null value) you’ll see the previously mentioned error.
To resolve this, you’ll need to update the NULL handling logic on your report. Under Result Manipulation > SQL options, change the Replace NULL by setting to NULL.
For more information, see this article: Using drill-in to refine your report.