Hey, Loop! There’s been some issues with the microphone with Heroes of the Storm in the past and currently with Catalina.
This issue is primarily with the access permission for the microphone not prompting properly. These workarounds that may help prompt the permission:
- Try forcing Windowed mode and see if the prompt may be appearing in the background when attempting to use the microphone.
- Try going to System Preferences > Security & Privacy > Microphone and allow access for Heroes.
If you are on MacOS Catalina, here’s the thread where a few users are helping each other out with some workarounds that are not supported by Blizzard due to some advance terminal commands needed.