MAC won't shut down

Hello Dave,
We regret for the inconvenience caused. We would request you to repair the AVG Program and check for the issue once, if the issue persist please let us know, we are here to help you. The following article http://support.avg.com/SupportArticleView?urlname=How-to-repair-AVG explains how to repair AVG program:. Thank you.

I just installed the free AntiVirus on MAC OS 10.11.6 and ran a scan.  After the scan my computer won't shut down, I have to turn it off with the power button and restart.   Why?  Is there another setting I need to tweak not covered by the installation?

Dave, Otherwise if that doesn't help… Mac OS support… Please click on the following link (http://avgclick.me/AVGtechnical) and choose Yes for the Question "Are you currently using any paid/trial AVG products?" inspite of using the Free version and fill out your details, select as Mac OS then the name of AVG Program that you installed in your device and in description please completely explain about your issue and finally click on the 'Start Chat' option. You will start a live, online chat with one of the AVG agents. 
AVG Guru

Hello Dave,
We regret for the inconvenience caused. We would request you to repair the AVG Program and check for the issue once, if the issue persist please let us know, we are here to help you. The following article http://support.avg.com/SupportArticleView?urlname=How-to-repair-AVG explains how to repair AVG program:. Thank you.