In the Inventory Manager, all QR/Bar code is identified by #LS prefix. First of all, the QR/Bar code reader should be configured to add this prefix when reading a QR/Bar code. How to Set up the #LS Prefix for your Scanner.
Make sure your keyboard layout is set to US English; otherwise, QR code and barcode scanning will not work properly inside the Inventory module.
To configure the prefix, follow the instructions in the following Setup Guides: