Hardware: late-2012 Mac Mini OS: El Capitan 10.11.4 (SIP is DISabled) Safari 9.1 (only user-installed extension is AdBlock 2.54) I'm trying to install either "ClickToFlash" or "ClickToPlugin", and neither one will install. What I'm doing: - download either extension to the desktop - double-click the ".safariextz" file to launch installer - dialog box appears: "Are you sure you want to install the extension "ClickToPlugin" ? - I click the "Trust" button...and... - nothing. At this point, the Safari "extensions" pref pane is displayed, but nothing new has been added. What am I doing wrong? RESOLVED! A little more investigating found the solution. These extensions won't install UNLESS you reboot into Safe Mode first. Don't know why that is, but it is what it is. ALSO... I previously had Safari Technology Preview installed. After booting to Safe Mode, I double-clicked the extensions, and... instead of installing into Safari, they installed to Safari Technology Preview instead. So... to get them to install into Safari, I had to first delete Safari Technology Preview. And I thought things like this were supposed to be EASY on the Mac. Ha! And one more thing: I tried to mark this thread as "resolved", but could not find the controls by which to do so. How do you do it?