Nothing happens when choosing Install in Chrome

Chrome browser shows the extension of Norton Security Toolbar v.2015.5.0.121.  When viewing what is in the webstore, the item presented as the extension Norton Security Toolbar v. 2015.5.4.11; but when I click on the button on the page for Install in Chrome,  nothing happens.  NOTHING CHANGES, and no announcements of any kind occur, and I still have the version 2015.5.0.121 of Norton Security Toolbar.  I also tried disabling the currently installed norton toolbar extension but same thing - meaning nothing happens.