VXGI Error

Hello guys, VXGI stopped working when i launching ue4…

Fatal error: [C:\UnrealEngine-4.19-VXGI-Blast-HairWorks-Flow\Engine\Source\Runtime\Windows\D3D11RHI\Private\D3D11NvRHI.cpp] [Line: 257]
VXGI Error: Creating a shader for VOXELIZATION_PIXL_SHADER set failed. PermutationIndex = 2, Hash = 0x40781634. (GI_ShaderFactory.cpp, 397)

Can anyone who can tell me why?

Thanks!