There are a couple of reasons why your ads are not validating. (Getting credits)
1. When you log into your account DO NOT bypass the "log in ad". Always click on "NO THANKS, TAKE ME TO MY ACCOUNT" link first before you start reading paid emails.
2. When you login to your account and is asked to "UPDATE YOUR ACCOUNT INFORMATION", please do so. Scroll down to the bottom of the page and click on the "SAVE" button -- then proceed on to reading "Paid Emails".
3. Another reason for your emails not validating is a browser issue. If you are using the newer version of INTERNET EXPLORER, this may cause some issues, though not always. Please try SWITCHING TO FIREFOX or GOOGLE CHROME browsers. This usually fixes the problem.