Hi,
If you have a problem with barcodes in sambaPOS then its possible that they start with number "zero",
When added as new products, sambaPOS accepts the leading "0" but when salesman wants to sell product, sambaPOS doesn't recognize this leading zero (even though it is in the database), I verified the problem, to find out that when adding products to sambaPOS it accepts leading zero but at the interface of the salesman it removes the leading zero and thus does not recognize the product !
to fix this I had to edit all the entries of those products and remove the leading zero from thier barcodes.