Change 333136 had a related patch set uploaded (by Nschaaf):
Fix hang on no results and add helpful message

https://gerrit.wikimedia.org/r/333136

Change 333136 merged by jenkins-bot:
Fix hang on no results and add helpful message

https://gerrit.wikimedia.org/r/333136

@Capt_Swing There should now be more helpful error messages when results don't show up.

In T155650#2954777, @schana wrote:

There should now be more helpful error messages when results don't show up.

Specifically, the error message is:
{"message": "Seed item is not in the embedding or no neighbors above threshold."}

As discussed in the research showcase, the reasons that articles don't appear in the embedding can vary between them not receiving above a threshold of pageviews in the preceding month or not having any neighbors in the embedding above a specific point.

Does that provide enough background, @Capt_Swing?

@schana this is great. Thank you!