How to make a simple API-call?

[#1]

Hi.

I've managed to retrieve a qlikTicket using the server certificate authentication method and with the code sample from the link below:

Connecting to the QPS API using certificates ‒ Qlik Sense

https://help.qlik.com/en-US/sense-developer/2.2/Subsystems/ProxyServiceAPI/Content/ProxyServiceAPI/P...

Now I'm trying to make a simple call to the QRS to retrieve some general information. These are the GET-requests I've tried:

https://[servername]:4242/qrs/about?Xrefkey=[Xrefkey]&qlikTicket=[qlikTicket]

https://[servername]:4242/qrs/about?qlikTicket=[qlikTicket]

https://[servername]:4242/qrs/about?Xrefkey=[Xrefkey]

In the GET-header I've added X-Qlik-Xrfkey.

I've also tried omitting the port number, thinking communicating with the proxy is the way to go as described here:

QRS API URLs ‒ Qlik Sense

https://help.qlik.com/en-US/sense-developer/2.2/Subsystems/RepositoryServiceAPI/Content/RepositorySe...

However, in all cases I'm getting "403 Forbidden" from the server.

What is it that I'm missing here?