Got this working by going into the Settings Editor, clicking on xfce4-mixer and changing both /active-card and /sound-card to PlaybackBuiltinAudioAnalogStereoPulseAudioMixer. Before that, active card was HDA Intel Alsa Mixer. Essentially, this works the same as the workaround in comment 3, except it is the GUI version of doing things.
Got this working by going into the Settings Editor, clicking on xfce4-mixer and changing both /active-card and /sound-card to PlaybackBuiltin AudioAnalogSter eoPulseAudioMix er. Before that, active card was HDA Intel Alsa Mixer. Essentially, this works the same as the workaround in comment 3, except it is the GUI version of doing things.