It turned out that the Windows 10 update 1803 introduces (or changes) a privacy setting which prevented me using team speak/voicechat in games. To fix, you can just need to open All Settings -> Privacy -> Microphone or search Microphone and find it in the list. It needs to be enabled and apps need to be allowed.
Thanks to MicroSip for pointing this out on their site! I discovered this fix while using MicroSip on some Asterisk testing.