i have 2 macs, both on the same version of Sierra; both with the same OS settings. but on my 12" macbook, i can't open notification center with a key command. i've rebooted (of course). changed the key command several times. quit NC in activity monitor. it opens from the menu bar, but am so used to 'command-option-N'... it's frustrating. and it works perfectly on my 13" pro. anyone else seeing this? or have an idea for a possible fix? thanx!