When I point my camera at a QR code, it does not acknowledge it. Why is this?

Open the Code Scanner from Control Center

1. Go to Settings > Control Center, then tap. next to Code Scanner.
2. Open Control Center, tap the Code Scanner, then position iPhone so that the code appears on the screen.
3. To add more light, tap the flashlight to turn it on.

Scan a QR code with your iPhone camera - Apple Support (IN)