results from a SPARQL query are not shown

[m1ci]

When submitting following simple SPARQL query, no results are shown.
This is essential, as this is very simple query which should definitely work.

PREFIX databus: <https://dataid.dbpedia.org/databus#>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX dct: <http://purl.org/dc/terms/>
PREFIX dcat: <http://www.w3.org/ns/dcat#>
PREFIX sec: <https://w3id.org/security#>
PREFIX cert: <http://www.w3.org/ns/auth/cert#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX databus-cv: <https://dataid.dbpedia.org/databus-cv#>
PREFIX dbo: <http://dbpedia.org/ontology/>

SELECT * WHERE {
  ?group databus:account ?account .
}

Looking at the HTTP response, the data is provided to the client, but it is not displayed.