Have you already authorized 3D Flag? If not, try applying Flag this way:
1. Add a checkerboard layer to Motion. Select it.
2. In the Library tab, open the Filters> Zaxwerks folder.
3. Click on the 3D Flag filter.
4. Then click on the Apply button at the top of the Library panel (that is, don't drag the filter over, use the Apply button).
If the effect is authorized, it should be applied to the checkerboard. If not, the authorization dialog will be displayed.
Let us know if this works and if you still have problems.