There is no such program as listed in your title
Should this message be moved to Premiere Elements
[moved to Premiere Elements]
With so little information I can only take a guess. Premier Elements, nor any other NLE, holds the video clips within a project. Instead, it "indexes to" or "references" the source material where it was when the media is added to the project. When the source is moved, deleted or changed, Premier Elements is lost and can't proceed.
Depending on where the source media is, you may be able to establish a new link. Or, you start over from scratch.