Unfortunately at this time we've taken our video file functionality out of rotation for some tune ups. This feature will return in the future better than ever.
Any existing video clips inside of your projects will be unaffected, but we will be unable to restore any deleted video file layers once they’re gone.
For now though, you should still be able to bring in video clips with the help of 3rd Party Integration layers in your project space. See: "But wait there's more" section on our Blog Post.
Also be sure take a look our Lightstream Roadmaps which is a public board where users can submit and vote on ideas they'd like to see added to Lightstream.