1. There is a mistake in the barcode print, such as voids or spots
2. The quality of the barcode print is low, for example low contrast
3. The surface is too glossy or with too little contrast
Some of the problems can be alleviated by improving the lighting conditions for the barcode scan. Low contrast is a bigger problem in poor lighting.
You may experience that other devices are able to scan the barcode, and some devices are not. This is due to differences in the technology of the camera which is used to scan the barcode.
In order to fully determine if the quality of the barcode is acceptable or not, dedicated hardware is needed which can measure the quality parameters of the barcode. If the barcode cannot be scanned by the Qarma app, it does not necessarily mean that the barcode quality is not good enough, but it should be checked further with dedicated hardware.