Checkout: Google Checkout (HTML API)
All you need to do is to configure both your Google Checkout merchant account and the plugin. Follow the few simple steps below.
PLEASE NOTE that if you have a live Google Checkout account, you should login at http://checkout.google.com/sell/ but if you are using a sandbox account for testing purposes, you should login at http://sandbox.google.com/checkout/sell/ .
1. Google Checkout Configuration
Go to your Google Checkout merchant panel and navigate to Settings > Integration where you will see all the integration settings.
Untick/uncheck the checkbox that says “My company will only post digitally signed carts” to turn off this limitation and allow unsigned carts as specified in the HTML API documentation.
Next you should insert your API callback URL setting which is the absolute URL to your shopping cart page of your WordPress site with “?wpcomethod=coreturn&type=google_checkout” appended to it.
So if your shopping cart page URL is “http://www.domain.com/shopping-cart/” then the API callback URL will be “http://www.domain.com/shopping-cart/?wpcomethod=coreturn&type=google_checkout”.
IMPORTANT: It is very important that you fill in the API callback URL correctly so please review the API callback URL and ensure that it is accurate according to the URL on your site.
Next step is to select the 3rd radio button for the ‘Callback Contents’ which says “Notification as HTML (name/value pairs)”.
By default, Google Checkout doesn’t charge customers’ cards immediately so it logs the order and you have to click the “Charge” button in order for Google Checkout to notify the plugin that an order has been paid for.
To prevent this extra step and have Google Checkout communicate with the plugin immediately, before the customer even returns to the site, you can turn on automatic charging. Go to Settings (tab) > Preferences in the Google Checkout account and choose the 2nd radio button “Automatically authorize and charge the buyer’s credit card”.
2. Configure the WordPress Shopping Cart plugin
Login to your WordPress dashboard and navigate to Checkout > Configuration > Google Checkout Settings where you will see the Google Checkout settings for the plugin.
First, fill in your Merchant ID and Merchant Key which you copy from your Google Checkout merchant panel under Settings > Integration where you configured Google Checkout in Step 1 above.
Last step is to turn the ‘Sandbox’ setting On or Off based on your Google Checkout account. If you are using a live account, you should turn it off and if you are using a sandbox/test account, you should turn i on.