Do you need change your server?
For a new MS SQL Server, after a restore a back-up, you cannot connect?
How are doing your MS SQL users
To detect Orphaned users:
USE <database_name>;
GO;
sp_change_users_login @Action='Report';
GO;
To Resolved:
USE <database_name>;
GO;
sp_change_users_login @Action='Report';
GO;
-- Associando a um login existente:
EXEC sp_change_users_login 'Update_One', 'nome do usuário', 'nome do login'
-- Associando a um login existente:
EXEC sp_change_users_login 'Update_One', 'servicedesk', 'servicedesk'
Troubleshoot Orphaned Users (SQL Server) English
https://msdn.microsoft.com/pt-br/library/ms175475.aspx Brazilian Portuguese