I keep running into issues when creating forms where some barcodes work and others do not. On one form impaticular, I can't seem to get the barcode to be readable at all. I have tried everything from changing the width, height, and quiet space around the barcode. All but two barcodes work on this form and the data is not significantly different between barcodes. The barcodes I am having trouble with are Code 128 with text longer than 6 or 7 characters. Any suggestions?
As with most of the 1D barcodes, the trick is to ensure the barcode is wide enough to hold all of the data you are putting into the field itself. If you over populate the barcode the modules will be thinner and the space between them also thinner. These may work when you print from a laser printer and scan the test page immediately but running them through a real workflow won't work (ie: print on an ink-jet printer on low-quality paper, then fax).
You can generate Code 128 barcode with encodable text more than 6 or 7 characters, but the generated Code 128 barcode can not be read. Do I understand your question right? Then I think you have to find the problem with your barcode reader. Some barcode readers have limits on its scannable size.