First, Do you see the Dell Rewards $$$ on your AWA profile? If not, sometimes you need to wait a few days for it to be applied to your account. I've had it happen to me where I redeemed Dell Rewards $$$, but it doesn't show up, so I emailed the AWA support desk and they applied it to my account the next day.
Second, if you are in the USA, did you use this link to sign up for Dell Rewards: https://www.dell.com/en-us/lp/dell-rewards-program (I didn't create a new Dell.com account from the homepage, I created it through the rewards program link)
If so, I recommend speaking to someone on the Dell.com site and explaining the situation. Fortunately they have a Live Chat feature :) Hopefully they can look into your account to make sure everything is setup correctly.