You typically get this error when the server expects a particular file (like the tiff for a page) to exist at a location but it's not there.  Either the server is looking in the wrong place, or your move operation missed some files.  It's unlikely that the Laserfiche server is looking in the old volume location, but you might try restarting the service just to be sure.  The next step would be pinning down a file that appears to be missing and seeing if it's there.  If you find a problematic document, Properties | Page Info will give you the relative volume paths of where those files should be.  You can look at that location on the file system and see if the file is indeed there or not.  I think you would get a different error if the file is there but the LFS service account doesn't have permission to read it, but that's something else to verify.