Blank Notification Banner Stuck in macOS Sierra
I had stuck notification w/ request to change password. And I killed it:

➜  ~ ps -ef|grep -i notif
    0   121     1   0 27Sep19 ??        38:04.27 /usr/sbin/notifyd
133241192  1067     1   0 27Sep19 ??         2:06.70 /System/Library/CoreServices/NotificationCenter.app/Contents/MacOS/NotificationCenter
➜  ~ kill 1067