There can be several reasons for a file failing to load.
The specified media files can no longer be found.
A removable or network drive may no longer be available, or the project file may have been saved on another computer.
If you wish to move projects between several computers, you will need to backup your project.
If any media cannot be found by the project, you will need to locate the media on your computer, and either add the media back into the project or restore the media to the directory that the project expects it to be found.
The media files may not be valid.
Images or video you are trying to load may either be corrupted, or in a format that PhotoStage does not yet recognize.
There may not be enough memory available to load the desired media.
Some images or video may not be able to load if the dimensions of the media are extremely large.