A discussion can stall because its participants are answering different questions. One person may be describing what happened while another is arguing about what should happen next. Before adding another opinion, identify the question the group is trying to resolve.
Useful questions are specific enough to invite an answer. Instead of asking why everything went wrong, ask which decision created the present difficulty. Instead of demanding agreement, ask what evidence would change the current view.
Leave time for a response. A question delivered as a disguised accusation usually encourages a defence, while a sincere invitation makes uncertainty easier to acknowledge. Your tone and willingness to listen matter as much as the wording.
At the end, restate what has become clearer and what remains open. A productive conversation may finish with a better question rather than a shared conclusion. That is still progress when it helps people understand the issue more accurately.