The database page shadowing function could not use the contents of the existing file. Restart recovery using this file is not possible.
The server attempts to start without having the database page shadow file available.
The database page shadow file contents are not valid. This can be caused by: a partial write to the page shadow file itself, the file being manipulated by a process outside of the server, the file being overlaid by a different file, or the file could have been erased.