Hi Community,
You may be confused if you are arriving here via search. This post is a different issue than for "importing" a clip into the timeline (and either audio or video didn't follow). As a quick fix, click the V1 and A1 boxes at the far left of the Timeline, then drag once more.
Why is this happening? See this post: can't drag video to the timeline
A quick anecdote about the nomenclature of editing might be in order, as using proper terminology is very important in video editing and motion graphics:
The correct terminology is to edit a clip into the timeline. One does not import a clip into the timeline, one imports a clip into the project.
Thanks,
Kevin