If your calls start failing when using a Bluetooth headset for LeadDesk on Windows 11, the first thing to try is a restart of your PC.
Particularly try this if the headset had previously worked, and seemed to stop working for "no reason". If you check the console, this problem is characterised by the error Requested device not found.
Why this may work
While there are other causes for this kind of problem in LeadDesk, one possibility is having the wrong headset profile selected.
Bluetooth headsets may have two profiles: One for music, with better quality sound, but the microphone switched off, the other with slightly lower quality sound, but the microphone enabled.
In earlier versions of Windows, you would see them listed as separate audio devices to choose between. In Windows 11, the different profiles are hidden, showing as only one audio device and switching invisibly between these profiles as the user changes between uses.
Occasionally, however, the automatic switching does not happen correctly. This can result in LeadDesk not being able to find a headset even if it had worked perfectly earlier in the same day.
A restart will reset the automatic switching and enables the correct profile in LeadDesk again.