Some GroupShareKit Questions

Hello,

I have some questions regarding to the GroupShareKit.

I installed the ASP Sample Project. Somehow I cannot query the users. I always get this:

 404 - File or directory not found.

The resource you are looking for might have been removed, had its name changed, or is temporarily unavailable.

The Problem is caused in this line: 

var gsUser = await gsClient.User.Get(new UserRequest(userName));

I get a token so there is a connection to the server. We are running only MultiTerm 2015. Is a full Version of GroupShare required? Or is it a problem with the users? Or do we need Version 2017 for this?

Thanks for your help.