As far as I understand it (and in simple terms) Liftoff defaults to browsing communities on Lemmy.world as a guest , even if you are signed into your account on a different instance. In your case Lemm.ee
At the top of the page you’ll see a drop down. If you change that to your instance Lemm.ee you’ll be able to comment and vote.
Personally I would like to see this behaviour changed as it’s highly confusing for someone new to Lemmy who isn’t on Lemmy.world