Make sure your microphone is securely plugged into the headset. The port can accept the microphone boom in two directions, however we recommend the arm is pointing up.

Check that the mute button isn't turned on or the sound bar lowered down.

If the issue isn't coming from these, then you can check if you misconfigured the sound input settings. 

Head to System Preferences > Sound, and then click the “Input” tab. You should see a list of devices you can use as a sound source, the headset/microphone should show up within the list.

- To use a device, such as “Internal Microphone,” click it.  You should see the bars fill up next to “Input Level” as you speak.

- If you don’t see anything, increase the “Input Volume” slider and try speaking again. If the slider is too low, your Mac won’t detect any sound.

- Whether you’re using an audio interface or if you have previously chosen a different setting, select it from the list.

- If a movement happen in the “Input Level” indicator, we are on the right track.

If the issue remains, we would advise you to check your Microphone Permissions.

Apple has an expanded permissions' system, and it may prevent apps from accessing the microphone until you allow it.

Head to System Preferences > Security and Privacy > Privacy, and select “Microphone” from the sidebar. There will be a list of apps that have requested access to your microphone. Any you have approved will have a checkmark next to them, while those you’ve denied will not.

Click the Padlock icon at the bottom left to authenticate with your admin password (or Touch ID, or Apple Watch prompt). You can then approve or deny permission as you see fit by checking or unchecking the boxes next to the apps.

If the following troubleshooting tips don't sort this out, there might be an application that is creating the issue, kindly try the following:

You can try checking the app’s preferences to see if there are separate settings for input devices. Apps like Adobe Audition and Audacity allow you to specify an input device separate from the one selected in the audio “Input” settings under “System Preferences.”

If everything seems fine, try deleting and reinstalling the app. Look for an updated version to download, just in case the issues were caused by incompatibility. Apple has made serious changes to the macOS permissions system over the last few revisions, so some outdated apps might not work.