SQL Server FILESTREAM access denied

I have my machine and a database server on the same Windows domain. I also have a staging machine that is not on the domain.

From my machine, I am able to perform any and all operations using FILESTREAM without trouble. From the staging machine, my application is able to use TSQL as it pleases, but the moment it tries to open a SqlFileStream, I receive 'access is denied.`

The staging machine, the database server, and my machine all have a local user set up with an identical name and password so that the application can use integrated security to connect to SQL Server. Since FILESTREAM is the only thing not working for the non-domain machine, I am wondering if I am missing something in the FILESTREAM documentation or if the documentation fails to specify that only Active Directory will suffice for integrated security, or of course if there is something I can do to make my situation work.