Not all phones' cameras are equal, and some phones will have a harder time reading the QR code. If you're struggling to read the QR code, you can try with the 2nd QR code. One is located inside your lock (smart controller) or on its back (rim/mortice strike), and the other one is in the leaflet that came with the code. The one in the leaflet is the preferred one as it is bigger. Whichever QR code you're using, it can also help to have a uniform background. Try placing the leaflet/lock on a piece of white paper before scanning. It also helps to have the QR code well and uniformly lit.