I've been using KDenlive off and on for about two years now and I'm having a new problem. When I add an effect,(greyscale, noise reduction,ect)it used to show up on the clip monitor that I would then use to adjust the effect. Now the effect doesn't show on the clip monitor.The monitor just shows the video clip as if nothing has been added. When I render the clip, it renders the clip with the effect.
I can't see the effect preview to make adjustments before rendering. I'm sure that I've messed with a setting that has turned the preview off. I just can't think of how the fix it. Any ideas?
Thanks.

Tell us, is Menu > View > Project Monitor ticked?

As far as I know the effects are only visable in the Project Monitor and not in the Clip Monitor.
So, you have to be sure that this Project Monitor is selected in the View Menu like normcross says.

Project monitor....project monitor.....project monitor,yeah I knew that. I was just testing you. That's the story I'm sticking to.
Thanks for the help.