KB001677: Why Does Double Clicking with the Mouse in the Chromatogram not Display the Spectra? - MS ChemStation 

This is due to Data analysis option being selected. Position the mouse cursor on top of the chromatogram.
If the cross ( + ) shaped cursor appears, this indicates manual integration mode. From the [Tools] menu, click [Options] to open the [Select Data Analysis Options] window and then clear the manual integration check box. The cursor changes to a vertical line ( | ), indicating mean spectra mode. Double clicking on the data in the chromatogram screen in this mode displays the spectra.