Python cgi script can't copy to or modify items on file server

I'm working on an application to be used on our intranet.  It needs to be able to create directories and move files to our file server (N:), and to eventually modify them.  Currently, I'm testing it using IIS (localhost) on my computer.  I'm a novice at IIS by the way.   Okay, I'm using a python cgi script and it is unable to do this...

driveLetter = r'N:'
    picDir = os.path.join(driveLetter,r'FieldPics') #set output directory as N:\FieldPics   
    
    picCountyDir = os.path.join(picDir, str(county[0])) #set output directory as N:\FieldPics\CountyName 
    if not os.path.exists(picCountyDir):
        os.makedirs(picCountyDir) #if necesssary create the county directory inside the N:\FieldPics directory

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It tells me, "The system cannot find the path specified."   I have given IUSR and NETWORK SERVICE full control of N:\FieldPics.  I'm unable to figure out what I need to do next.