How to test messaging properly and convince leaders to change messaging that is not resonating?

Ah, if you're going through this right now, I feel you. This one is tough and it's because messaging can be so subjective sometimes. If you can, try to take the conversation back to two things:

1. Data-driven insights: Emphasize the importance of data-driven decision-making. Use concrete data from A/B testing, customer feedback, and performance metrics as much as you can to showcase how the two options are performing.

2. Customer-centric focus: Highlight the significance of aligning messaging with the needs and preferences of the target audience. Explain how the new messaging not only resonates emotionally but also addresses the functional benefits that matter to customers. Showcase testimonials or case studies demonstrating how customers find the new messaging more appealing, thus enhancing their connection with the product or service.

And if that doesn't work, come to a compromise and keep an eye on the performance of the messaging so you can bring it back up again after some time to re-evaluate.