I don’t know how to do active Language Reactor by Youtube.
(have restarted mac 2 times. Still doesn’t work )
Otherwise, I can use LR by webpage and find it’s great.
Thanks for your help 
@Heya Hello! 
Make sure you have this extension installed https://chromewebstore.google.com/detail/language-reactor/hoombieeljmmljlkjmnheibnpciblicm?hl=uk
You should see it in the extensions popup, here:
