Win 10 Home, AMD FX6300, ASUS Radeon R9 270X, audio-capable HDMI cable connected to this HDMI audio extractor switch. Yes, I've tested other ports on the switch and other cables. Everything works with other devices, just not my PC.
In Sound Settings, only my onboard sound card shows as an available output device. In the troubleshooter, it shows 6 devices labeled "(1-6) - Digital Display Audio - AMD High Definition Audio Device" that think they're unplugged: "The connector for this device is located in the HDMI connector."
Last week, I rebuilt my PC after a hard drive crash, so the environment is pretty clean. I let Windows install the AMD drivers, but that didn't include the audio drivers. I just installed the Adrenaline edition software v18.8.1, and I get the same result. As this thread suggests, I've tried reverting the PCI Express Root Complex driver to the Microsoft PCI Bus driver, but no change.
What's my next step?
Edit: I booted the PC from a Linux live distro, and the HDMI out to the splitter works perfectly, so I've ruled out the possibility of any hardware issues.
Edit2: I realized that the PCI Bus driver was causing random hard freezes, so I reverted that change.