Recently after updating to the latest February security patch, I noticed that a key feature of SWIPING DOWN FROM ANYWHERE TO ACCESS NOTIFICATION PANEL is not working.
settings>display>homescreen>enable swipe from anywhere to open notification panel or restart your device once or remove 3rd party launcher or theme and try again..
This is a bug. Actually after restarting it will work for a while and again it will not work. So you have to restart your phone again. Somehow Goodlock app has created this issue.