I'm trying to add Google Checkout to my magento 1.7.0.0 shop. I've traced the issue and it seems to fail during posting to google's server because when I try to read the response it's false.
The error I get is: Google Checkout: Invalid response from Google Checkout server
I'm using magento 1.7, google sandbox with sandbox credentials, verified bank account, unchecked digitally signed carts, but am using a self-signed certificate on my development machine, and API version 2.2.
The issue is happening in app/code/core/Mage/GoogleCheckout/Model/Api/Xml/Abstract.php on lines 174, 175
$http = new Varien_Http_Adapter_Curl();
$http->write('POST', $url, '1.1', $headers, $xml);
$response = $http->read();
There was a problem with it being a local environment. The issue was either with Google not being able to communicate or with my tld ending in .dev. Possibly Google rejected the request for that reason.