A Logitech Wireless Headset H800 on Win10x64 v. 1709 Pro connects through its proprietary leave-in nano receiver on a USB2 port and uses the Microsoft audio endpoint driver v. 10.0.16299.15 on a Gigabyte Z97X-Gaming G1 mobo. No later version is available for the driver.
The volume is stuck at a painful maximum, and using the headset's volume control will not lower the volume. Neither will reducing the volume with the slider control in the tray, or the Volume Mixer. Enhancements are off. Manage Audio Devices | Playback | USB Audio Device | Properties | Levels did not alter the volume.
Rebooting the PC also did not resolve the problem. Neither did deleting the wireless headset in Device Manager and letting it re-find the device. There were and are no yellow bangs or red x marks there. A search on this device found no relevant question, here, on other website of reliability, as well as at Microsoft's site.
How might I troubleshoot further?