Scanning QR codes on our iPhone is really simple and does not require any third party. Through these QR codes we can, for example, connect to a Wi-Fi without the need for the password . And it’s thanks to the camera that we can simply point to a code and… that’s it. But what about when the system doesn’t want to work? We can do several things.
Focus and go, more or less
Before seeing configuration options, the best thing we can do is turn off our iPhone, wait 15 seconds and turn it on again. This should fix any errors. It is also a good idea that by opening the Settings app , entering General and Software Update, we verify that our iPhone is updated to the latest version of the operating system available.
If the Camera app still does not want to recognize a code, the first thing we can do is make sure that the option to scan and read QR codes is activated in Settings. Just open the Settings app , go to Camera , and turn on Scan QR codes .
Something else to keep in mind is that in order to scan a code, we need the camera to be in photo mode . Neither the video mode nor the portrait mode have this possibility, so we must slide to the right or left to place ourselves in Photo mode. 
Let’s also try to focus the code well. Sometimes maybe zooming in, sometimes avoiding some reflections on glass or shiny surfaces that can make part of the code hidden. All this, without forgetting that some custom codes only work in certain apps . Examples of them are codes for payment applications or loyalty cards. 
If none of this works, it might be a good idea to invoke the scan function directly from Control Center . Remember that we can add it there by opening the Settings by entering the Control Center and touching the “+” next to “Code Scanner”.  Once this is done, just slide down from the top right of the screen and touch the button in the form of a QR code to scan one. 
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If none of this works, something really weird, by all accounts, and we can’t scan any QR codes, the best we can do is reset the iPhone and test that it works . If it does, but stops working after restoring the backup, our only option is to set up our iPhone as new. If it doesn’t work after the initial restoration, we should go to an Apple Store so they can help us.