Hello Greg Duffield,
Barcode readers have a maximal resolution at which they can operate properly. You should check the specification of your barcode reader. If the individual bars and spaces of your barcodes are too narrow, the barcode reader might not be able to read them correctly.
If you have set the Stretch property of the Barcode report item to true, and the size of the barcode is too small, the bars and spaces will be shrinked accordingly, in order to make them fit in the given space, thus making them too narrow to be read by the scanner. Try setting the Stretch property to false, and adjust the Module property instead. The value of the Module property determines the thickness of the narrowest bar or space within the barcode, so it cannot go outside the maximal resolution supported by the barcode scanner. Then you can adjust the size of the Barcode report item manually in the Report Designer. Set the Value property to some string that is long enough (i.e. 22 characters). If the barcode cannot fit the given area, an error message will be displayed. Adjust the size of the report item in the designer, so that the actual barcode reappears again.
On a side note: what export format are you using for printing? In some formats the barcodes are rendered as raster bitmaps (due to limitations of the particular format), which sometimes might not produce sufficient quality for printing. Probably the best export format for printing barcodes is PDF, because it uses vector graphics to render them, that scales well with the printing resolution.
the Telerik team