English ivy produces adult leaves and flowers only when it grows vertically. Horizontal growth is vegetative and produces juvenile leaves. Juvenile leaves are also produced when the plant grows vertically, but at some point in its vertical life, it also produces adult leaves and flowers.
According to reports that I’ve read from seemingly reliable sources, it may take ten years or more for the vine to flower, at least in the Pacific Northwest region of North America where I live. That sounds about right with regards to my ivy. It didn’t produce adult leaves or flowers for a long time, even when it was growing vertically, but now it flowers and produces fruit every year.