When using Geo Targeting a small array with your location data will show up in the Geo settings. Make sure this shows actual (partial) geo data. If something is wrong with the server or lookups an error may show there instead.
If you’ve recently changed settings, quota’s or geo service you may have to remove the ‘adrotate-geo’ cookie in your browser. The location in the array is stored there.
Removing the cookie and then reloading any page with Geo Targeted adverts or resaving the settings will generate a new cookie and thus new geo location data.