The Volumetric Shader seems broken when used along the Niagara Mesh Renderer.
Reported and tested in version 4.25.3(CL 13942748). Tested with same result in version 4.24.3(CL 11590370).
Result: The material will refuse to compile and give you these errors:
MaterialEditorStats: Error: [SM5] /Plugin/FX/Niagara/Private/NiagaraMeshVertexFactory.ush(791,2-66): warning X3206: implicit truncation of vector type
MaterialEditorStats: Error: [SM5] /Engine/Private/VolumetricFogVoxelization.usf(64,33-110): error X3004: undeclared identifier 'VertexFactoryGetTranslatedPrimitiveVolumeBounds'
Expected: The material compiles properly
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-98030 in the post.