If you used one of their codes, then I recommend writing them again with the explanation that it *was* their code. Sometimes it takes a couple emails to get action.
For those who have used discount codes from other sources and gotten your cash back, you've been lucky.. It is clearly stated in ebates' TOS that using codes from other sources will forfeit your cash back.
I understand the frustration. I'm still wrestling with ebates over an Orbitz purchase of Disney tickets. Even though they we're purchased and paid for in full back in May, I have to wait until 40 days after I picked them up in Sept. to request my cash back. They absolutely WILL NOT do anything until that time, even though many people have posted that their purchases have posted within 3 days of placing their ticket order.
OP, if you want cash back on your purchases, here are plenty of sites that will do it. Ebates has been around a very long time and generally has a good reputation. Upromise also has a good reputation and longevity. MyPoints also works well for cash ask but you do better to redeem for GCs with them. I would stay away from start-up rewards companies that promise big payouts. They tend to disappear in the middle of the night, along with the cash that you earned.