When I ran the \client subfolder's UpdateInstaller.exe on several Windows 7 computers yesterday, I noticed that none of the May updates got installed.
I reviewed my WSUS Offline Update download logs, and none of the May patches were listed. Thinking that there might have been some delay in Microsoft releasing the patches, I tried downloading again this morning. Same result - no May patches.
I searched the web and found numerous references as to the cause. Many people have noted that the plain text "Microsoft Security Notification Service" bulletins released towards the end of April 2016 contained this statement:
"Effective as of the May 2016 security bulletin release, all Windows updates will be available only via the Microsoft Update Catalog (http://catalog.update.microsoft.com/), and will no longer be available on the Microsoft Download Center (http://download.microsoft.com/). Making the updates available from only one location simplifies the process for our customers of finding and downloading security updates."
WSUS Offline Update needs to be rewritten to start using the Microsoft Update Catalog instead of the Microsoft Download Center. If that's not possible, WSUS Offline Update will no longer be of any use (at least to me).