Cannot publish files stored on partition other than C

Hi I have Server 2012 with RDS, also I have some C and D partition, currently I am using RDS to enable access to some excel

worksheet that employees use, but when I try to edit permissions for that C:\Folder where Excel is, I get 

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Error Applying Security 

An error occurred while applying security information to :

C:\Folder\file

Failed to enumerate objects in the container. Access is denied.

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Then my thoughts were that MS restricted access to C: so I wanted to move that excel file to D: partition, and I had no problems with permissions, but during application publishing I receive :

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You must specify a file from the RD Session host server server.domain.local by using UNC path . Example \\server\c$\path\filename ....

If the problem persist, ensure that the following Windows Firewall exceptions are enabled:

1) File and print sharing (SMB-OUT)

2) File and print sharing (SMB-IN)

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Firewall is configured OK, but in example of the UNC paths it says \\server\c$\path\filename , does this mean that I cannot publish files that are on the D: partition ?? 

Also how then to solve permission problem described above ??

Thanks