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I suspect that the issue you are hitting is that there are two Wellingtons: Wellington, Victoria and Wellington, New South Wales. Without a State field in the view to specify whether this is Victoria data or New South Wales data, Tableau is not sure which one you are referring to.
A similar issue, with a solution, is described in the following article:
If you do not have a State field in your database, but all of your data will be from Victoria, another way to solve this is to create a calculated field with content "Victoria", set the geographic role of the field to be state, and place that in the details shelf. This will act as a State field for you.