Everything seems to work but it does not backup Lotus Notes (.nsf) files

I the “files option” and not the “category option” in my WD Smartware. It works OK but does not backup the .nsf files, that are exactly the most important ones in my Notes. I checked the file selection and the Notes directory is selected. None of the files are open so it is not the problem. The “reason” the software presents for not backing up is “Files pending backup”, that is obvious but does not explain the problem. Any ideas?

Make sure no other program is accessing the files at the time of the backup