Please help me about continuity grated out

I use MacBook Air 2018 with OS Mojave and iPad 2018 iOS 12.1

Already update in os and page keynote app.

I try to use continuity from camera to MacBook.

In my MacBook, the insert from iPad is grayed out as picture.

I search from community and try

-turn off/on both wifi and bluetooth
-sign out/in Apple ID both MacBook and iPad
-delete all caches at ~Library from macbook

-delete bluetoothlist from preference
-connect bluetooth, link between MacBook and ipad

but they are useless for my problem. plz suggest me.thank you