Check if area is covered for traffic flow

Question

I am testing the API on a brand-new freemium account. It works as expected for a few examples but it returns 204 No Content for an area I am interested in.

Where can I look up if an area is covered or not?

curl -v \
  -X GET \
  -H 'Content-Type: *' \
  --get 'https://traffic.ls.hereapi.com/traffic/6.1/flow.json' \
    --data-urlencode 'bbox=35.8730,14.5108;35.8655,14.5189' \
    --data-urlencode 'apiKey=RH2**************************ACis'
Note: Unnecessary use of -X or --request, GET is already inferred.
*   Trying 34.255.189.0:443...
* Connected to traffic.ls.hereapi.com (34.255.189.0) port 443 (#0)
* ALPN, offering h2
* ALPN, offering http/1.1
* successfully set certificate verify locations:
*   CAfile: /etc/pki/tls/certs/ca-bundle.crt
  CApath: none
* TLSv1.3 (OUT), TLS handshake, Client hello (1):
* TLSv1.3 (IN), TLS handshake, Server hello (2):
* TLSv1.2 (IN), TLS handshake, Certificate (11):
* TLSv1.2 (IN), TLS handshake, Server key exchange (12):
* TLSv1.2 (IN), TLS handshake, Server finished (14):
* TLSv1.2 (OUT), TLS handshake, Client key exchange (16):
* TLSv1.2 (OUT), TLS change cipher, Change cipher spec (1):
* TLSv1.2 (OUT), TLS handshake, Finished (20):
* TLSv1.2 (IN), TLS handshake, Finished (20):
* SSL connection using TLSv1.2 / ECDHE-RSA-AES128-GCM-SHA256
* ALPN, server did not agree to a protocol
* Server certificate:
*  subject: C=NL; ST=Noord-Brabant; L=Eindhoven; O=HERE Global BV; CN=traffic.ls.hereapi.com
*  start date: May  5 08:29:46 2020 GMT
*  expire date: May  6 08:29:46 2021 GMT
*  subjectAltName: host "traffic.ls.hereapi.com" matched cert's "traffic.ls.hereapi.com"
*  issuer: C=BE; O=GlobalSign nv-sa; CN=GlobalSign RSA OV SSL CA 2018
*  SSL certificate verify ok.
> GET /traffic/6.1/flow.json?bbox=35.8730%2C14.5108%3B35.8655%2C14.5189&apiKey=RH************s HTTP/1.1
> Host: traffic.ls.hereapi.com
> User-Agent: curl/7.71.1
> Accept: */*
> Content-Type: *
> 
* Mark bundle as not supporting multiuse
< HTTP/1.1 204 No Content
< Accept-Ranges: bytes
< Content-Type: application/json
< Date: Sat, 27 Feb 2021 15:10:20 GMT
< ServedItems: 0
< Server: openresty
< time: 233
< Vary: Accept-Charset, Accept-Language, Accept
< X-NLP-TID: ea69440d-5689-49af-89c9-a6c1538b4725
< X-REQ-MODE: flow-small
< X-Request-Id: REQ-c99544f8-7776-4bb4-9d25-8f148dec8fc9
< X-Served-By: i-04b5db781c349303a.eu-west-1a
< Connection: keep-alive
< 
* Connection #0 to host traffic.ls.hereapi.com left intact