verification failure

This is my first attempt at this and it's not going well...
wsusoffline was downloaded and unzipped. The update generator launches fine. It starts extracting files when the start button is pressed on the download screen. The process is short-lived as the message 'ERROR: Catalog file ..\client\wsus\wsusscn2.cab signature verification failure' appears and the process terminates. Another dialog box appears with the message "Error downloading/ verifying updates for w61-x64-glb. In the log file there are some additional messages.
WARNING: Integrity database ...\client\md\hashes-wsus.txt not found
INFO: Downloaded/validated most recent windows catalog update file
WARNING: Deleted unsigned file "C:\Users\Michael\Downloads\wsuupdate\wsuoffline\client\wsus\wsucsscn2.cab
ERROR: Catalog file ..\client\wsus\wsusscn2.cab signature verification failure.
There is no anti-virus program installed.
I've also tried it with the Verify Downloaded Updates box unchecked. It does run to completion. I'm thinking that's probably not the best of choices but I've found threads where that's recommended so maybe that really is OK. Fortunately the computer, a Toshiba C855D-S5202 laptop, isn't really used for anything more than a learning tool so it's no big deal if it's necessary to flush it and start over.
Thoughts? ...and thanks!
Michael
wsusoffline was downloaded and unzipped. The update generator launches fine. It starts extracting files when the start button is pressed on the download screen. The process is short-lived as the message 'ERROR: Catalog file ..\client\wsus\wsusscn2.cab signature verification failure' appears and the process terminates. Another dialog box appears with the message "Error downloading/ verifying updates for w61-x64-glb. In the log file there are some additional messages.
WARNING: Integrity database ...\client\md\hashes-wsus.txt not found
INFO: Downloaded/validated most recent windows catalog update file
WARNING: Deleted unsigned file "C:\Users\Michael\Downloads\wsuupdate\wsuoffline\client\wsus\wsucsscn2.cab
ERROR: Catalog file ..\client\wsus\wsusscn2.cab signature verification failure.
There is no anti-virus program installed.
I've also tried it with the Verify Downloaded Updates box unchecked. It does run to completion. I'm thinking that's probably not the best of choices but I've found threads where that's recommended so maybe that really is OK. Fortunately the computer, a Toshiba C855D-S5202 laptop, isn't really used for anything more than a learning tool so it's no big deal if it's necessary to flush it and start over.
Thoughts? ...and thanks!
Michael