mute bluetooth headphones

since updating to 1909 i cannot mute my headphones. when i click on the toggle, the 'X' appears instantly, beeps, then disappears.

I'm not to sure how to fix this problem but on Bose forum I found a post with your same device and similar issue

NC700 Microphone Mute Doesn't Work Properly - Bose Community - 219826


Solved: NC 700 does not mute - Bose Community - 223142

I had similar problem, I could not mute my Bluetooth headphones, also I could not even turn the volume down to 0% when my Bluetooth headphones were connected. For me, the problem was with Bluetooth Absolute Volume in Windows 10. Bluetooth Absolute Volume is feature in Windows 10 that combines PC volume with Bluetooth audio volume which was introduced with Windows 10 update 1803. You can find more about Bluetooth Absolute Volume in Windows 10 on these links: Reddit, Microsoft answers.

To fix the problem I disabled Bluetooth Absolute Volume. To disable it you need to edit Windows Registry "DisableAbsoluteVolume" which is in "Computer\HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Bluetooth\Audio\AVRCP\CT". To disable Bluetooth Absolute Volume set "DisableAbsoluteVolume" to "1". You can find detailed instructions on how to disable Bluetooth Absolute Volume in Windows 10 on these links: Windows 10 Forums, YouTube.

Remarks:
1) Before editing Windows Registry, it is always good to backup your registry. (Links: Microsoft Support, YouTube.)
2) After editing Windows Registry you need to restart your PC before changes take effect.