1. Check your system’s microphone settings in Windows Settings > Privacy > Microphone and make sure permission is granted.

2. Check your audio recording application's sound input settings. Tip: Make sure it's the same sound input device selected in Windows Settings > Sound devices.

3. Test with Microsoft's sound recorder app (Windows Settings > Voice Recorder).

4. Restart your computer and try again.

5. Uninstall and reinstall the OneNote app.