My Mac is configured to shut down every night at 10:30 pm but it never does, even if absolutely no program is running. There is also no error message - it just does not shut down. It is also configured to start up every day at 6 am, and that it does (when I have shut it down manually which is working very well). I don't know when exactly this started, probably just some weeks ago, or even only after upgrading to OS X 10.11. What could cause this and how could I fix it?