my mission control isn't working
I downloaded this app called nwea its an testing app for my school exams. and after I downloaded this app my mission control didn't work. what I'm saying about mission control is you use three fingers to swipe up and u can see all the website u are currently using. anyways I searched it up on google and I found out two ways. first one was to go to terminal and kill all docks and it didn't work. the other way was to go to activity monitor and quit the dock (GUI way). on the keyboard it also has this Botton(f3) and that doesn't work either. is there any other solution, or do I need to go to apple store to fix this. by the way my laptop is MacBook air 13.3-inch (1440 x 900), Intel HD Graphics 6000 1536 MB graphics, 250.79gb(storage), memory is 8 GB 1600 MHz DDR3.
MacBook Air, macOS High Sierra (10.13.5)