Basically slaves need to see shared assets (they need to have path pointing not on Your "D:\" drive but to shared network address i.e. "\\192.168.1.1". They still can be in Your "D:\" drive but sharing settings and paths matter here)
I understand that this is difficult to understand so illustration:
I have some maps for models used in the scene and want to render that in distributed rendering.
As You see they are pointing to D:\... drive and that path is invalid for all other rendering nodes in my networked PCs.
Though they are in the shared folder and can be accessed in alternative paths:
and mapped drive "L:\"
These 3 paths are all valid for my local workstation, but only 2nd paths is valid in my entire network. But since I have mapped L:\ drive in all of my networked PCs pointing to my Library folder
The last path is what I am using for my assets: "L:\Models\Vizpeople\BirchTrees\textures"
Now it is important to make sure that materials maps used point to either "\\192.168....." or "L:\" path so it can be rendered correctly in all DR nodes:Same applies for XRef objects used in the scene.
This is just one of few ways how to configure network shares for distributed rendering.
Hope this is clear to understand and helps in Your situation.Note:
Or You need to check transfer missing assets.