“It looks like another app is already using the camera” (0xA00F4243)

You'll see this on Windows if you try to switch an app back to your built-in webcam while FaceReady is running — the Camera app calls it error 0xA00F4243 and tells you to close other apps. Nothing is broken. The “other app” is FaceReady.

Why it happens

Windows gives a physical camera to exactly one app at a time. While FaceReady runs, its engine holds your webcam open continuously — that's how it takes the years off live, frame by frame. So your real webcam genuinely is busy, and any app that asks for it directly gets told so. Every virtual camera on Windows works this way, including OBS.

What to do

If you want the de-aged you: don't switch back — pick FaceReady in the app's camera menu. That IS your webcam, improved, and it's the whole point.

If you want the raw webcam back: quit FaceReady (check the system tray — closing the window may leave it running). The instant it quits, the physical camera is released and every app can use it normally again.