Mask Tool Button Always Grayed Out

The Mask Tool Button on the toolbar (just to the right of the Text Tool Button) is always grayed out and never selectable. Keyboard shortcuts to create a mask are also not working. Oddly, I can use Object->Convert to Mask with no issues on an existing shape.

Any help would be much appreciated. I am new to FCP X and Motion 5, but have advanced understanding of video and picture editing.

Late 2012 21.5" iMac | OS X Yosemite 10.10.4 | Motion 5.2.1

Make sure you have an actual layer object selected and not a group or a text object. For those you can use a Image Mask.

Please let me know if that helps