When you run csvimport, what it really does is create scan files and inserts them in to ManagementSuite\LDSCAN folder. Any scans that don't process properly are placed in \ManagementSuite\ldscan\errorscans. Delete all scans from errorscans and then try the import again. The check errorscans for rejected scan files. There should also be accompanying error messages in the Core Server application event log.