This site is just a data mining site at this point. They regularly send out surveys that "glitch out" upon completion or are otherwise rejected upon completion.
Customer service is basically no help at all and they just respond with the same canned responses over and over. They just tell you to give them the specific survey code so they can look into it but these conveniently disqualified surveys do not even show up in your list, effectively giving you no way of reporting specific surveys.