Digital Audio Not Working

I am having problems getting S/PDIF and HDMI audio working on Ubuntu 15.04.

The S/PDIF output shows up in "System Settings > Sound", but no sound is outputted. The HDMI output does not show up.

I have tried executing the commands in Step 1 in https://help.ubuntu.com/community/SoundTroubleshootingProcedure, but they do not fix the problem.

Here is the output of the alsa-info.sh script: http://www.alsa-project.org/db/?f=76f5134bf711a2727fa56d1d7ec582945fc6944c

Here is the output of aplay -l:

    **** List of PLAYBACK Hardware Devices ****
    card 0: HDMI [HDA Intel HDMI], device 3: HDMI 0 [HDMI 0]
      Subdevices: 1/1
      Subdevice #0: subdevice #0
    card 0: HDMI [HDA Intel HDMI], device 7: HDMI 1 [HDMI 1]
      Subdevices: 1/1
      Subdevice #0: subdevice #0
    card 0: HDMI [HDA Intel HDMI], device 8: HDMI 2 [HDMI 2]
      Subdevices: 1/1
      Subdevice #0: subdevice #0
    card 1: PCH [HDA Intel PCH], device 0: VT1802 Analog [VT1802 Analog]
      Subdevices: 0/1
      Subdevice #0: subdevice #0
    card 1: PCH [HDA Intel PCH], device 1: VT1802 Digital [VT1802 Digital]
      Subdevices: 1/1
      Subdevice #0: subdevice #0
    card 1: PCH [HDA Intel PCH], device 2: VT1802 Alt Analog [VT1802 Alt Analog]
      Subdevices: 1/1
      Subdevice #0: subdevice #0

When I run aplay -D plughw:0,3 /usr/share/sounds/alsa/Front_Center.wav, I get

    Playing WAVE '/usr/share/sounds/alsa/Front_Center.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Mono

However, no sound actually plays. The same happens for devices 7 and 8 of card 0, and device 1 of card 1.

Any ideas where I can go from here?