[Page Plus 9 - the non printable guidelines for columns, margins and text frames have disappeared]

Hi, using Page Plus for desk top publishing.  Normally when I set up columns, rows, margins and text frames, the outline appears as a non printable guideline.  Mid-way through one project those guideline have disappeared, so the display shows how it would look when printed.  Example below - normally the text columns would have greyed guidelines.  Presuambly I have inadvertently turned off an option, but can't restore it.  Any suggestion would be much appreciated.