Follow these steps to ensure your microphone inputs are set up correctly in order to use OMS Communications (voice control) scenarios.
Check your input settings
Select Start > Settings > System > Sound.
In Input, go to Choose a device for speaking or recording, and select the device you want.
To test your microphone, speak into it. In Volume, make sure the blue bar moves to make sure Windows hears you.
Check your input settings for the OMS app
SelectSettings > Privacy > Microphone.
Make sure that the toggle switch for "Allow apps to access your microphone" is turned on.
Check the list of apps that have access to the microphone and ensure that the apps you're having trouble with are listed and have access.
Troubleshooting Tip:
Try an external microphone. Generally people have more success with Communications scenarios (especially in crowded places) with an external microphone (for example on a set of headphones).
Note: if you are using an external headset / microphone, ensure that is selected as your input device on your PC (see Step 1 above).