Updated avast to the latest version 2015 and since then even though avast is scheduled to run a scan every day at 12pm, its not. its now 12:15 and my scan still has not happened.
Try a repair…Control Panel>Uninstall a Program>double click “avast”>click “repair”>reboot 
That did nothing, still not working
do a search… there’s several threads on this… IDK if anyone ever resolved it
I did a search, nothing comes up, and it was working with the previous version, 2014 I forget the whole version name of the previous version, if I knew this was going to happen I wouldn’t have upgraded
I ended up uninstalling and reinstalling, scheduler now works.