Safari 10.1.1 software update for MacOS Sierra 10.12.4 won't install

There is another post describing this same issue on El Capitan that is marked as solved. The solution was to turn off caching on a local proxy server and try installing the update again. I don't have a local proxy server on my network. Any other possible reasons for this issue?

To recap what was said in the other post, the App Store app shows the Safari 10.1.1 update as available. When I click on the update link, a progress bar starts then quickly disappears. The update button may then be grayed out.