It might be doing exactly what it normally does. Try running your movie and see if it plays.
When you create a timeline mask, the mask layer and the layers that it masks are automatically locked (look at the locks next to the layer name) and the contents are visually active as masked layers. If your mask is used to gradually reveal, until you run the file, it is not revealing anything. If the mask is being used to limit a viewing area then with the layers locked you would see the mask working to reveal only that area even without running the file.
If you unlock the layers you should be able to see things again.
Thanks for your reply. I played the movie and it does not show anything. I have tried text and drawing objects and then adding a mask layer above the object layer, but when the layer becomes mask everything disappears. If I unlock the layers I can see the objects, but when the layers are locked the objects disappear. I did this once already and it worked. I have no Idea why is not working now I have not moved any of the settings.
I just drew a line using the brush tool. I added another layer above named it mask and drew a square. I added 20 frames on the time line, then I right clicked on the mask layer and checked mask. As soon as I did that both layers locked and disappeared. If I unlocked them the appear again. Is there a way I can attach a FLA file here? Thanks.
You can't attch files in the forums, but you can include screenshots. So far what you describe still sounds normal, except when you said you ran the file and saw nothing, but that too i ssubject to seeing what you have done for the animation.