Report not recognizing data source

I successfully added and tested the connection for a data source. I created a Layer Report and set the data source (an ArcGIS service for parcels). The data source showed up in the Field List panel, but it wouldn't expand to show the fields.

I also tried creating a blank report and adding a data source. I clicked "Next" after selecting the parcels data source, but then it got stuck on the "Loading..." message. Unfortunately neither Chrome developer tools of Fiddlers gave me any clues as to what's going on.

The issue seems to be that I can create data sources, but they're not binding to the report. Can anyone give me some ideas on things I can try next?