Forum Post: C# GetApplication returns null with Peachtree 2008

I am creating an automated import of Purchase Invoices for a client who is using Peachtree 2008 Premier, and I've downloaded Sage 50 2016.0 SDK. I'm using the credentials that were provided when I downloaded the SDK and the function returns NULL. When I use the credentials of a current user, the function causes a Not Authorized error. I have searched the computer for the Interop.PeachwServer.dll and I cannot find it. So, is the SDK backwards compatible with their version (15 internally)? What options do I have available to me? public static IApplication ApplicationLogin( string pUserName, string pUserPassword) { ILoginSelector lLoginSelector = new LoginSelector (); ILogin lLogin = lLoginSelector.GetCurrentLoginObject() as ILogin ; return lLogin.GetApplication(pUserName, pUserPassword) as IApplication ; }