I use the Scan QR code feature of iOS fairly regularly. It really is handy to just scan a QR code instead of typing in a lot of information on that tiny keyboard. Apparently, some people’s QR code feature is turned off by default, possibly after an iOS update. If your QR code feature is not working on your iPhone, then here is how to reactivate it.
The place to activate the QR code feature is, of course, in Settings.
Once in Settings, scroll down and tap on the Camera icon.
In the upper area of the Camera settings, you will see “Scan QR codes”.
If this is off, just toggle it to the “On” position.
Then, test it by scanning a QR code. If it still does not work, a Restart of your iPhone should fix it once and for all.
The QR code feature is great, but it is not helpful if it is not activated.