1) The barcode reading function is not enabled

2) The barcode does not conform to the specification, For example, there is a lack of necessary blank space, the comparison between the bar and the empty space is too low, and the width ratio of the bar and the empty space is not appropriate

3) In direct sunlight, the photosensitive device enters the saturation area

4) The barcode surface is covered with transparent material. Although the eyes can see the barcode, the handheld device has strict reading conditions and cannot read it

5) Hardware failure, contact with after-sales personnel for maintenance.