I've been hammering on the zero buffer issue for days. For me it will return results...but the results are outlandish. For a selection of just a few parcels, a zero buffer returns 50 pages of labels. I've tried the develop branch and there's no relief. Also, aside from the zero buffer issue the correct parcel selection doesn't show up on the screen. The labels get generated for all the parcels despite not being displayed. I'm thinking it must be a data related issue since it seems to work with the esri data/services. I'm going to try eliminating all overlapping polys next to see where that gets me. It'd be wonderful if esri ported this functionality to an AGOL solution. These kind of apps are cool, but can be very difficult to get working right. Let me know if you figure anything out.
Update:
I edited the infoWindow.js file to get this working for me. I did a find/replace substituting the LOWPARCELID with PARCELID everywhere it occurred in the file. I'm not entirely sure why the code doesn't use something that is unique and invariably populated like OBJECTID instead of LOWPARCELID here, but it must need a text field. In any event, maybe this tweak will work for others who are having the zero buffer issue.