Do your logfiles contain any errors? Please could you post the output of the following files:
Code:
/googlecheckout/logs/response_error.log
/googlecheckout/logs/response_message.log
I can't 100% remember what Sandbox does in terms of ordering, It could well be that the order is not processed/no emails sent/items still in the cart as the order hasn't actually been processed - I will double check.