Seen it twice now, different audio hardware. After Windows 11 upgrade, audio shows working in Device Manager, but does not actually work. So far, the solution is to get into Device Manager, and delete the driver items for the hardware which should be working, from both “Software Devices” and “Sound, video and game controllers”. Then reboot. After the reboot, both times, it created two new sections at the top for audio, and then sound began working fine. Here’s an example:
