All materials missing after Datasmith import (Unreal 4.20.3)

Hello! I’m a beginner with Unreal. I’m doing a project, where I have to convert forest scene from 3ds Max 2017 + Vray to Unreal 4.20.3.

I downloaded Datasmith plugin, which work nicely with newest Unreal 4.50. I got all the geometries and textures right. But when I try to import that same Datasmith to Unreal 4.20.3, all textures (or materials) are missing. I can see all the textures in Content Browser, but there’s only one material, which is only VrayLight material from 3ds Max (Taustataivas). And because I haven’t use Unreal before, I have no clue, how to link all the materials back in the scene. Textures seems to be in Textures folder, please check the screenshot I attached.

I also tried to open that saved Unreal 4.50 scene by clicking right mouse button and choosing “Switch Engine 4.20”. I got many errors about plugins, that doesn’t work with that old Unreal version and when the project was open, it was empty. There wasn’t geometries or textures at all.

Could you please help me? Please say that there’s simple solution to get materials back in scene.

Thank you!