There are several possibilities here.

1. Check that the model of Grabba is capable of reading that barcode symbology.
2. Check that the symbology is enabled in software. You can do this by going into the Grabba Driver options, to the Barcode area, and then to Barcode Symbology Options. If you have a custom written application then you should also check with your software developer.
3. The barcode is too fine pitched, printed poorly, or damaged. Check your barcodes, Often the barcode will finish off the label or too close to the edge. Remember if you cant see all of the barcode at one time neither can the scanner. Sometimes changes in barcodes mean you need vary the distance from the barcode to the Grabba. Try varying the distance from the Grabba to the barcode from 25cm (1 inch) to 150cm (6 inches).