If a network scan does not return any results, it usually means the machine IP addresses being scanned could not be reached (or not reachable when pinged) or have an open port. 

If the IP addresses you're trying to scan are indeed valid, do the following:

  1. Select Scans > Scan List.
  2. Select the scan from the list.
  3. Under the Settings tab, select the Additional Settings tab.
  4. Clear the Ping Hosts checkbox. Note: Disabling this parameter will cause scans to take longer to complete.
  5. Select Modify. Try the scan again.