Process not using fonts

I'm trying to print Chinese characters in a PDF generated by an exe process (phantomjs). However these characters end up as "?". The process is created in a Worker Role in C#.

When creating the same process manually in a cmd-window on the same virtual machine, everything works fine.

The Chinese language pack is installed, however, from the same admin account that can successfully create the PDF by hand.

In order to make sure all users see the same fonts from the language pack, I added the settings to all system users on the machine as described here.

The proces is started from C# like this

Process.Start(new ProcessStartInfo
{
    UseShellExecute = true,
    FileName = "phantomjs.exe",
    Arguments = "pdf.js"
});

So how can it be, that my manual cmd-window process uses the Chinese fonts properly, but not the process started by C#?