LINE error 404: no default richmenu

The get default rich menu ID endpoint (GET /v2/bot/user/all/richmenu) found nothing to return. The documented 404 row is simply "The default rich menu isn't set." The endpoint only reports the default rich menu set with the Messaging API; it doesn't look at per-user links.

This is a state, not a fault. Common reasons are a channel that has never set a default through the API, a default that was cleared with DELETE /v2/bot/user/all/richmenu, or a default whose rich menu was deleted. Users may still see a rich menu even when this endpoint returns 404: a per-user rich menu linked through the API, or a default configured in LINE Official Account Manager (which this endpoint reports as owned by another channel instead).

If your code reads the default menu to decide what to do next - for example to diff it against the menu it is about to deploy - treat 404 as "none set" and continue, rather than as an exception.

// If the default rich menu isn't set (404 Not Found)
{
  "message": "no default richmenu",
  "details": []
}

Make setting the default rich menu an explicit, idempotent deploy step, and never delete a rich menu that is still the default without first setting its replacement. Monitoring that calls this endpoint daily catches the case where someone clears the default by accident and users fall back to a Manager menu or none at all.