I added a web part to a page I created for a site collection sub-site having the project template. I am able to add a web part (Media & Content -> Page Viewer), but the Web Part Properties button on the Web Part tab is not enabled to edit its properties. The web part has focus and I am logged in as the administrator. What is required to enable the Web Part Properties button?
SharePoint 2013 SP1 Enterprise Edition, Windows Server 2012 R2, IE 11.