??
If you mean it just won't read the media width, make sure the media is lined up straight and in the right location. There should be a sticker on the back of the machine where the media feed rollers slide around on the bars. Make sure the left roller (closest to the capping station) is lined up with the decal correctly. If the media is loaded too far left or right you'll get a media sense error.
Or are you getting something else?