hdmi output appears to be muted

pcm0: <Realtek ALC671 (Rear Analog)> at nid 20 and 27 on hdaa0
pcm1: <Realtek ALC671 (Analog)> at nid 33 and 24 on hdaa0
pcm2: <Intel Kaby Lake (HDMI/DP 8ch)> at nid 3 on hdaa1
cat /dev/sndstat
FreeBSD Audio Driver (64bit 2009061500/amd64)
Installed devices:
pcm0: <Realtek ALC671 (Rear Analog)> on hdaa0 kld snd_hda (1p:1v/1r:1v)
pcm1: <Realtek ALC671 (Analog)> on hdaa0 kld snd_hda (1p:1v/1r:1v)
pcm2: <Intel Kaby Lake (HDMI/DP 8ch)> on hdaa1 kld snd_hda (1p:1v/0r:0v) 
default
No devices installed from userspace.
dev.hdaa.1.init_clear: 0
dev.hdaa.1.reconfig: 0
dev.hdaa.1.gpo_config:
dev.hdaa.1.gpo_state:
dev.hdaa.1.gpio_config:
dev.hdaa.1.gpio_state:
dev.hdaa.1.gpi_state:
dev.hdaa.1.config: forcestereo,ivref50,ivref80,ivref100,ivref,vref
dev.hdaa.1.nid3_original: 0x18560010 as=1 seq=0 device=Digital-out 
conn=Jack ctype=Digital loc=0x18 color=Unknown misc=0
dev.hdaa.1.nid3_config: 0x18560010 as=1 seq=0 device=Digital-out 
conn=Jack ctype=Digital loc=0x18 color=Unknown misc=0
dev.hdaa.1.nid3: pin: Digital-out (Jack)
      Widget cap: 0x0040778d PWR DIGITAL UNSOL 8CH
     Association: 0 (0x0001)
         Pin cap: 0x09000094 PDC OUT HDMI DP HBR
      Pin config: 0x18560010 as=1 seq=0 device=Digital-out conn=Jack 
ctype=Digital loc=0x18 color=Unknown misc=0
     Pin control: 0x00000040 OUT
      Output amp: 0x80000000 mute=1 step=0 size=0 offset=0 (0/0dB)
     Connections: 1
           + <- nid=2 [audio output]

dev.hdaa.1.nid2: audio output
      Widget cap: 0x00006611 PWR DIGITAL 8CH
     Association: 0 (0x0001)
             OSS: pcm (pcm)
      Stream cap: 0x00000005 AC3 PCM
         PCM cap: 0x001a07f0 16 24 32 bits, 32 44 48 88 96 176 192 KHz

dev.hdaa.1.%parent: hdacc1
dev.hdaa.1.%pnpinfo: type=0x01 subsystem=0x80860101
dev.hdaa.1.%location: nid=1
dev.hdaa.1.%driver: hdaa
dev.hdaa.1.%desc: Intel Kaby Lake Audio Function Group

This HP Slimline can detect front and rear connections.
I doubt it can detect hdmi audio connections.  Why is my hdmi muted?  How can I un-mute nid3?
-- 
FreeBSD freebsd.friedrich.org 13.2-RELEASE FreeBSD 13.2-RELEASE releng/13.2-n254617-525ecfdad597 GENERIC amd64