Possible problems with ...

.. using colors
Do not invert the colors of your code.
Use high contrast colors for back- and foreground.

.. using colors on eyes
Try to use dark colors for the eyes of your Code.

.. using logos
If you upload a logo, try to move your logo up or down.
Try to lower the error correction rate to make your code work.

.. using too much information
If you create vCards or Codes with long URLs your Code may have too many pixels, so try to reduce the information or use our Dynamic Codes.