Mac Mini will not restart, cannot install updates (OS X El Cap 10.11.6) Something is preventing my Mac Mini (Mid 2011, core i5) from restarting. As as result, I cannot install updates. How can I find what is preventing the Mac from restarting?  

If I have to restart to clear out the RAM or similar, what I have been doing is running the terminal command sudo reboot now but I cannot install updates this way. Thank you.
Upgrading the OS to High Sierra resolved this issue.