This means that no scan requests were sent. When you registered crawl data, you may not have accessed any URLs that can be scanned. For example, you may have only accessed static (e.g. HTML and GIF) files, or you may have accessed the URL that is used to stop crawling immediately after the URL that is used to start crawling.
VAddy only scans GET and POST requests that have parameters. GET requests include parameters in the URL (e.g. “foo=aaa&bar=bbb”).