So I think i figured out what the issue was, in addition to leaving in ‘to’ instead of ‘from’ as I was testing everything I could think of. I actually have several custom post types created in addition to ‘event’ and ‘speaker’, including ‘location’ and ‘sponsor’. I was originally trying to query posts via the relationship of event_to_location. That was the one that wouldn’t return anything no matter what I did
I just switched the query back from speaker to location, and no posts returned again. But I went into the custom post types and compared the settings for each. My ‘location’ CPT had ‘exclude from search’ as true, but speaker was false. Sure enough, toggling the ‘exclude from search’ setting on breaks the display of MB Relationship posts. Is that expected behavior? I would expect turning off ‘publicly queryable’ would block the display. But not exclude from search?