Barcode scanner won't read printed labels
1. The printhead in your printer might be scratched (evidenced by thin white streaks through your print). This is common, and the most likely cause. Printhead must be replaced.
2. Material might be stuck on your printhead (usually evidenced by wide white streak vertically through print). Printing surface of printhead can be cleaned with rubbing alcohol and cotton ball.
3. The ribbon might be wrinkling due to uneven tension, producing intermittent diagonal streaks in your print. This is somewhat common, but doesn't fit your description as well as 1 & 2 above. Mechanical adjustment and/or proper media loading solves ribbon wrinkles.
4. Poor pressure and/or printhead alignment. Evidenced by grainy, light or no print on one side or the other of the media. This is somewhat common, but doesn't fit your description as well as 1 & 2 above. Mechanical adjustment solves printhead pressure and alignment issues.