All of our API resources will use surveygizmo.com in example calls, however, if you are using an EU account, your calls must use the surveygizmo.eu domain.
Not sure if your account is US or EU?
Check the URL when you are logged in to the application. If you see app.surveygizmo.com your account is a US account.
If you see app.surveygizmo.eu your account is an EU account.