Baked mask turns black/dark

Hello! Wondering if anyone knows why this is happening. When I bake a mask of a high poly object onto a low poly that already has a UV map imported in, it turns black. sometimes it happens and sometimes it doesn’t, so I am not sure… when I test it, it sometimes happens and sometimes doesn’t. Some meshes it happens to and some it doesn’t. Some meshes it will happen to sometimes and not others on the same mesh after different tries.