White text could disappear after processing a print job. This is often caused because the white text is set to overprint. If this is the case, the ‘white ink’ will be output on top of the inks below and the white text will disappear. Unless you are in packaging or use actual white ink in your production process, the white text should be set to "knock out".
When white text is used on a darker background, it should be‘knocked out’. The white text is literally knocked out of the darker background, which makes the paper show through.