You can't trap a voidwyrm with gates I recommend ( if you created a new surviver this won't work I think) but grab it with a skiff and with hn-la scan it and damge it with a weapen like a tek rifle or something else then with the skiff drop it when it's ready it tame with your mutagen put it in your last slot and tame your new Voidwyrm.

More Voidwyrm Taming & KO Tips