Watching Instantly Is Not Currently Available For Your Account. Unfortunately your account is restricted to streaming only within the 50 United States and its territories. You may still access your account, but you will not be able to play any title.
The reason is that your account is also used for ordering DVDs. In order to change region you have to disable the DVD option on your account by logging in to their website. Then go to Your Account > Your Plan and deselect the DVD plan.