You need to have a shape on the shape layer. Look at that little "Add:" arrow to the top and right of your screenshot.
Jeff Almosol's MasksToShapes script is no longer hosted in any of the links I know, including those links at the site referred to above. Does anybody know a location this script can be downloaded from?
This is really simple. Here are the steps for a never fail method that works with any version of AE that supports shape layers.
- Create a mask on any layer that has not been scaled, rotated or moved.
- Press the Ctrl/Alt + m to reveal the mask and set a keyframe
- Copy (Cmnd/Ctrl + c)
- Deselect all layers in the timeline and select the pen tool by pressing the g key
- Click anywhere in the comp window to set the first shape layer vertex
- Paste (Cmnd/Ctrl + v)
There you go. Works every time. Even works with animated masks. You get an animated shape layer.
Whished AE had poured this trick in a function with a name as well.