Did you get the congradulations page after you completed the survey?
Suggestions: clear your cookies and temp files BEFORE you begin doing surveys on a particular survey site. You will frequently be disqualified (DQ'd) for survey due to demographics; just keep trying until they run out of surveys or you get the congrads page.
When you get the congrads page, leave that page open for 10-15 minutes or until you received credit. It's rarely instant, but you will generally see a credit within 10 minutes. I usually have another tab open to my account page so I can check the status of the credit (need to refresh periodically).
If it hasn't credited in 10 minutes, take a screen shot of the congrads page, bring up the screen shot on your PAINT program, add a few notes so help you and FC remember what the survey is about (who/what/when) and save it to a jpeg picture. If you haven't received credit in a couple of days, send a support ticket to FC with the jpeg picture.