Insurance claim denial for flooding caused by neighbor's burst pipe

Our neighbor's pipe burst recently, which flooded our yard and basement. Our insurance is now denying the claim, stating that ground water flooding isn't covered. I have videos of the water actively flowing out of their house into our yard, but that doesn't seem to matter. I'm going to call their insurance and make a claim there, but I suspect that will also be denied.

Does anyone have any experience with how to navigate this? If our own pipe had burst, it would be covered. If the neighbor's burst pipe caused damage to their home, it would be covered. But since their burst pipe caused damage to our home, it's not covered? It doesn't seem right.

I appreciate any advice on this.