If effects are not showing in the video preview, they are most likely disabled in the Video Preview window. In the video preview window, open the "Split Screen View" menu by clicking the downward arrow.

This menu contains the following options: 

• FX Bypassed: Bypasses effects in the video preview playback.
• Clipboard: Shows the contents of the clipboard in the Video Preview window (and also the Video Scopes window).
• Select Left Half: Applies effects only to the left side of the preview for comparison purposes.
• Select Right Half: Applies effects to the right side of the preview. 
• Select All: Applies effects to the entire preview. 

Check to make sure "FX Bypassed" is not enabled.