Based on the situation in the sentence, select the most appropriate idiom.
Although Greta Thunberg gave a moving speech at the UN about environmental damage, it could ___________.

The conjunction "Although" signifies a contrast. Despite the speech being moving, it failed to influence or change the perspective of the policymakers. The idiom cut no ice means to fail to cause an effect or have any influence on someone.
Break the ice: To make people feel more comfortable in a social situation.

Walk on thin ice: To take a major risk.

Be the icing on the cake: An attractive inclusion that makes something already good look even better.