Never had that option checked. Also been my preference to open manually. I admit, I did chuckle about this because your usual reply is “you can’t replicate” because you were on Windows. Now I knew you were Mac and could try.
Firefox did work. Because of the nature of Reunion, import works but isn’t pleasing. There’s a demo o GedItCom II but only for 15 days so am waiting for final download I do. Never learned how to use it well but it’s “proper” GEDCOM (Reunion isn’t).