Materials not showing correctly on meshes from asset pack

Bought a pack from unreal marketplace which requires RVT to be enabled:
https://www.unrealengine.com/marketplace/en-US/product/stylized-grassy-fields-environment

Even after enabling RVT some of the materials still had issues. For the cliffs in particular(the asset I needed the most) the grass on the top is black. I had the same issue with another pack where it was blue instead. What’s the issue here?