A) If you have assigned the video in the past and "Archived it", you will have to "Un-archive it":
Like this, you can re-use the same videos you used last year by just un-archiving them. :)
B) If you never archived a video, then you can check the "Load More" button or the "Upcoming" lessons.
C) If you cannot find it, please contact us to firstname.lastname@example.org with the title of the video and the class it should be assigned to. We will take a close look and find a solution. :)