javax.net.ssl.SSLHandshakeException, installing certificate with keytool

Question

After reading the fix to this error:

Severe: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target

I did what the answer suggested. However the error is still there. To download the certificate I right clicked on the webpage I'm trying to make a request to and went through the steps in the screenshot below :

After using this command :

keytool -import -file <the cert file> -alias <some meaningful name> -keystore <path to cacerts file>

The certificate is indeed listed with :

keytool -list -keystore "%JAVA_HOME%/jre/lib/security/cacerts"

and the error appears when I do this:

public void getTopStream() {
    streamChannels.clear();
    String urlHitbox = "https://www.hitbox.tv/api/media/live/list?game=counter-strike-global-offensive&liveonly=true&limit=10&hiddenOnly=false&size=mid&showHidden=true";

    CloseableHttpClient hitboxHttpclient = HttpClients.createDefault();
    HttpGet hitboxHttpGet = new HttpGet(urlHitbox);
    try {       
        // hitbox.tv
        CloseableHttpResponse responseHitbox = hitboxHttpclient
                .execute(hitboxHttpGet);
        HttpEntity hitboxEntity = responseHitbox.getEntity();
        responseHitbox.close();
            }
        }

        // hitbox.tv
        if (hitboxEntity != null) {
            Scanner scanner = new Scanner(hitboxEntity.getContent());
            String strHitbox = "";
            while (scanner.hasNextLine()) {
                strHitbox = scanner.nextLine();
            }
            scanner.close();
            if (!strHitbox.equals("")) {
                hitboxTransformJSON(strHitbox);
            }
        }
    } catch (ClientProtocolException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

Any idea of what's wrong ?