The red placeholders don't indicate damage, only that your source content (video, images, etc.) either hasn't fully synced from the cloud, or can't currently be located (because your project didn't sync across all of your Adobe cloud-enabled devices, or you are signed into a different Adobe ID).
Please ensure that you are connected to the internet with a solid connection and that when you open your project, you give it enough time to FULLY SYNC before starting your editing. Look for the blue circle arrow in the corner near the Undo/Redo arrows... once it has made its complete cycle, you are synced and ready to begin editing.
Hope this helps! Make sure to press "✔ Correct Answer" on this post if this answers your question. Happy Creating! Anissa • @anissat