I am sure, you will be able to locate the download link, guess so you must be in a different page. Let me provide you the steps to locate the download link. Please log-in to Adobe.com > Open the Order History Page> Next to serial number of the purchased software, you will see a link named Download > Click on the Download button > Select Akamai Download Manager (Recommended)
Can you paste a screenshot of the download page when you try to download the order? Alternative you can download the trial version of Design Standard CS6 from here and while installing the software enter the serial number you would have received.