Conversations not showing in search results

I'm experiencing an issue where every other aspect of Search seems to be working as expected but when I do a search and select "Conversation" nothing ever shows. If I go directly to the results type page (conversationresults.aspx), I see a few things but not much. I'm not even sure where to start here. The result type exists and has never been modified. People search and all other types of search are working fine. I have no errors on any of my content sources.