The most likely issue is that the Geocoder API hasn't been enabled for the API key. Google has recently changed their developer accounts so that this feature isn't enabled by default. This can be done by following these steps:
- On the Projects homepage, click the Geocoding API link under the Unused APIs menu.
- When the Geocoding API detail page appears, click the 'Enable' button.
If that doesn't work, I'm currently working on a new version of the Geocoder plugin that will give more detailed feedback on any errors. Please can you send an email to firstname.lastname@example.org with the FTP and CMS login details for the site that is affected. Then I'll install this new version to get a better idea of the cause.
The most common cause of this error is:
- The plugin doesn't have an API key added to it.
- The Geocoder API hasn't been enabled.
- Security restrictions have been added to the key that stop it from working.
PHP Programmer - interactivetools.com