Paths and drives
If you are working with windows, then you probably use drive mappings (H:, P:,...) to access your fileserver.
And not UNC paths (\\fileserver\share\...).
You have to tell RR to map these drives.
If the rrClient and rrServer are running as service, then they are separate from the user logged in.
Services have to map their drives on their own. It does not matter if someone is logged in, who is logged in and what drives the user has mapped.
If you want to use multiple OS for rendering/submission, then you have to enter your project shares in this table.
Each OS has a different path to access the same file on your fileserver.
E.g. Your window path is \\\\Fileserver\\Share\\projects. On linux, the same path would probably me /mnt/share/projects.
If you send a scene from windows, the linux client requires to convert the path to linux before rendering.
If your Server runs on windows, but you submit and render on Linux, then the server has to convert paths. Otherwise it does not find rendered images.
Local Scene Copy has to be enabled for the job.