What to do when there is no HDMI audio device in playback device list?
a. Click right mouse button on the speaker icon in your system tray at the lower right corner.
b. Click Playback devices.
c. Click Right mouse button --> Show Disabled Devices --> select your TV -->Set Default audio device, and then press OK to confirm;
If it’s not helpful, please try step2.
d. Keep your TV on and the HDMI cable plugged in and Restart your Mini PC.