Generally, Test Studio will attempt to perform a 'get latest' from TFS when Test Studio opens a project. If Test Studio has a problem connecting to the server, there should be an 'Unable to connect to source control' error dialog. One way to find out more about whether a 'get latest' operation was attempted and what its outcome may have been is to check the application log. If you generate an application log for this behavior and attach it to this ticket, we may be able to find out more.
the Telerik team