No Codex-Search result on folio-snapshot

It seems that all Codex searches on http://folio-snapshot.aws.indexdata.com/ find zero records – even really simple ones such as "title starts with 'a'". For example, start a new session, click on Codex Search, set the query-index to "Title" and type "a" in the query box.

The query that's sent to the back-end is good, but the response is empty – not only of records, but of per-source diagnostics:

GET /folio-snapshot-109.aws.indexdata.com:9130/codex-instances?limit=30&query=%28title%3D%22a%2A%22%29%20and%20ext.selected%3D%22true%22%20sortby%20title

200 OK
{
  "instances" : [ ],
  "resultInfo" : {
    "totalRecords" : 0,
    "facets" : [ ],
    "diagnostics" : [ ]
  }
}

My suspicion is that there are simply no Codex sources registered on folio-snapshot.