Problems when scanning a QR code can often be resolved by adjusting the brightness of the screen of your mobile device. Please check whether some camera filters are on. For example, whether a "blue light" filter is set on your mobile.
If scanning still does not work, check whether you have the option of manually entering a code. This is often a serial number, which you can find on the product.
If you cannot solve it, please contact us. Do not forget to specify which product is involved and what exactly goes wrong. We will then gladly look for a solution.