Rendering in the cloud

what does this message mean?

Images are missing. If the image was removed or moved from the original path it was saved on your computer the link will be broken and it will be missing in the material

while working on this homework Revit crashed on me. Could it be that some images got lost then? and how would i retrieve it if yes?

Go into the material and see if it’s missing. If it is missing just reload the image in.