Tried in-game again, but still isn't working. I don't have any other multiplayer games with voice chat to test with, so not sure what else to try. Maybe have to try Helldivers support.
It may be that some application is taking exclusive control over your recording device, and therefore not allowing other applications to make use of the device at the same time. You can disable this for any/all of your Recording and Playback devices in the Sound menu of Windows.
Right-click on the VoiceAttack icon on the taskbar, and select "Recording Devices":
Next, select your recording device and click "Properties" ... select the "Advanced" tab along top, and then
Un-check the box shown below to disable exclusive control - repeat this for each recording and playback device you use:
Once this is done, you need to Restart Windows so that any applications holding control over any devices are released, and can start over with these new rules. DO NOT choose the option to "Shut Down" and then press the power button to start up ...
you want to specifically choose the power option to "Restart" otherwise the Windows OS will merely enter a hybridized sleep and then wake from it without changing anything.
Please let us know if this works, and if not, there may be other things to look into or try.