I`ve just brought an RL Motion Designer Elements pack “firework” into CTA2.
Above are a few screen grabs of what I did.
Suggest you check the file extension on your Designer elements vids.
If you bought your files from RL they should be in .popvideo format.
Quote from Content Store Motion Designer Elements page:
“How do you use popVideo?
For iClone users: Select the desired video from the Content Manager (or Explorer), then right click and drag the video to your main window and choose an import option (image layer, plane, billboard or background) from the menu.
For CrazyTalk Animator users: Select "Create Media" from the left toolbar, choose an import option (prop, image layer or background), then select the desired video from its location on your computer.”
If you bought your files from another source (as Jeff has already posted) they may require converting before they can be used in RL products. If this is the case I`m sorry but I have no personal experience to offer of that particular process.
Geoff.