I have made a film on movie maker but when I tried to add credits to the end, it wouldn't show them. I could type in all my credits but I have no preview in the panel on the right as you usually get. It also has a black screenshot on the storyboard and timeline.

When I tried to add a title, that didn't work either with the same results: eg/ black panel on storyboard, no preview etc

How can I fix this?