Error in create zip file

Apr 14 at 9:22 AM
Hello to all,
when I create a zip file from a folder with this code:
int segmentsCreated = 5;
            using (ZipFile zip = new ZipFile())
                zip.UseUnicodeAsNecessary = true; // utf-8
                zip.Comment = "This zip was created at " + System.DateTime.Now.ToString("G");
                zip.MaxOutputSegmentSize = 100 * 1024; // 100k segments

                segmentsCreated = zip.NumberOfSegmentsForMostRecentSave;


It returns, to click on the new store, the following error message:

the archive or is damaged or is in an unknown format (in Italian "Archive or is corrupt or in an unknown format").

What am I doing wrong? Graziee