Can anyone help me understand why some segments appear to return segment efforts via API, and others do not?  Using the same query, changing only the segment ID, one segment returns efforts and another does not.

When I view in the web UI, e.g. https://www.strava.com/segments/1234, I can see a recent effort (definitely within the time range).  Both activities are Followers Only, both are marked “downhill”, and I am properly authenticated.  I cannot tell any other important differences.  The only thing I can think of is that I have only done the segment that doesn’t work once, whereas the one that works I’ve done numerous times.

What’s more, if I manually find the activity view the web UI, and query /api/v3/activities/4321, I am able to see the segment effort contained in that JSON response.  

Any help appreciated.  Thanks in advance!

curl "https://www.strava.com/api/v3/segment_efforts?segment_id=$SEGMENT_ID&per_page=1&page=1&start_date=2000-01-01T00:00:00&end_date=2025-06-20T21:15:31" --header "Authorization: Bearer $TOKEN