I had two offers I didn't get the credits for,, the NPD Survey and the Pingo offer, I submitted support tickets and they responded in half a day. The NPD one I got credited right away and the Pingo one after I replied to a follow up emai. So both issues were taken care of in less than a day, I was pretty happy with that.
At least the support system seems to work. Even the peanut labs one, I submitted a ticket last night for one of their offers and I received the credits today.
Try using the support links, worked for me :)