If you are remote desktoped into your Qlik Sense server, the https://localhost:8590/masterlib/testpage will work. If you are accessing from a different system, accessibility is a function of what you entered into the installation when prompted for a friendly name that you connect to the server with. When you do this, a certificate and private key need to be supplied to the installer to allow GMS service to run with the fully qualified domain name (the last item in your list). If you followed these instructions and post install you are not able to access gms, then there is an issue with the service running the gms.
So, first question. If you remote to the server, can you access using localhost? If yes, then your issue is likely a certificates issue and how gms service is configured to run.
If not working, then look in services for the existence of Qlik EA Powertools Service Dispatcher service. If this entry is missing then the installer failed to install the powertools service dispatcher. If this issue, I can give you a batch file to install it.
If I remote into the qlik server and use https://localhost:8590/masterlib/testpage I am NOT able to access.
Checked the services and I DO see Qlik EA Powertools Service Dispatcher is in fact running.
So where does that leave me.