Sometimes, unknown locations can be prompted because there's a misspelling or another issue. When this happens, you can correct the unknown or ambiguous locations in your data using the Special Values menu. For that you need to follow a few steps:
- In the bottom right corner of the view, click the indicator of the special value that lists the number of unknown locations in your map. This opens the Special Values menu.
- In the Special Values dialog box, select Edit Locations.
OR you can also select Map > Edit Locations
This will let you clarify unrecognized and ambiguous values to locations in Tableau.
You can fix some ambiguous locations by specifying the Country/Region and/or State/Province for each city from a specific field in your data. After specifying the region I guess almost job is done.