We are running Magento ver. 126.96.36.199. On the admin page, there is no option under system for Magento Connect. We have an account with Magento Connect. Is there something that needs to be done to associate that account with the Magento Admin page?
Double check under
System -> Config -> Advanced -> Advanced that Mage_Connect is listed and enabled.
Another possibility, make sure you have the
downloader folder in your Magento root. I was missing this folder once, and just grabbed it from the Magento release at: https://www.magentocommerce.com/products/downloads/magento/