If you're using a Hytech USB 2.0 webcam , you might find that it doesn’t always work immediately upon being plugged in. While many modern webcams are "Plug and Play," older or budget-friendly models often require specific drivers to unlock their full resolution or enable the built-in microphone.
Discord sometimes conflicts with camera drivers. Go to Discord Settings > Voice & Video > Reset Video Settings. Then manually select "Hytech USB 2.0 Camera" from the drop-down menu.