Transitions in final cut express don't work. Help!

Does anybody know why the transitions that I drag from Effects to the timeline, they appear in the timeline but i can’t see the effect on canvas? Not even rendering nor making a clip. The strange thing is that if i have a clip, that I drag it from the Viewer to the Canvas (and I select “insert” “with transition”), it works very well and I can see it on the canvas. But it doesn’t work if I drag it directly from “Effects” to the Timeline. I appreciate your help.