reverse geocoding

I'm trying to get reverse geocoding to work:
i have add in configuration file:

    <entry key='geocoder.enable'>true</entry>
    <entry key='geocoder.type'>google</entry>
    <entry key='geocoder.processInvalidPositions'>true</entry>
    <entry key='geolocation.key'>Api-key</entry>

But when i click on show address then nothing happens no error to see.

in log i see:

Geocoding failed - Empty address - GeocoderException (JsonGeocoder:68 < *:31 < *:96 < *:93 < ...)

Try 'geocoder.key' instead of 'geolocation.key'
JB

great thank you