Whats the trick to making Sidecar work?

Didnt have the prefpane on first install so i followed the terminal command

defaults write com.apple.sidecar.display AllowAllDevices -bool true; defaults write com.apple.sidecar.display hasShownPref -bool true; open /System/Library/PreferencePanes/Sidecar.prefPane 

Now I have the prefpane. Ive paired a 5th gen iPad with iPadOS to bluetooth. Open sidecar and...... nothin. Airplay menu will sometimes show sidecar, but when i click it, it only shows my iPhone on iOS12 so it obviously wont work. Ive also tried plugging the lighting cable directly in to the laptop to the ipad and nothing. Is there some special trick to get it working?