I am referring to the interaction “Tab Select” which I have setup exactly like the tutorial (except without movement, only opacity) which works fine when clicking on another tab, but the closing interaction doesn’t activate. It looks fine when I click “Preview” in the interactions menu, but when previewing the site and trying, the closing interaction doesn’t activate.
No, you are not doing anything wrong. It is known bug, unfortunately.
BUT ONLY IN PREVIEW MODE. Interaction usually works fine on published site. Could you publish your site and check if it works?