The CXN can certainly play files at 24-bit/192kHz.
First make sure that the CXN is set to USB class 2.0 mode. This is done via the Audio settings menu on the front display.
Setup for PC:
Make sure to install the appropriate Cambridge Audio Windows 2.0 USB driver to your computer. Information on which driver to install can be found here. Once you have finished the installation go to the Sound menu in Control Panel and set the Cambridge Audio USB 2.0 product as the default output device.
Setup for Mac:
If you are using a Mac you will not need to install any additional drivers. Simply navigate to System Preferences >Sound and select the CXN as the output.
Information on advance settings you can amend can be found here.