Prime Opinion Does Not Credit Me After I Complete Some Surveys

For some time now, I have been using Prime Opinion; something strange continues happening. Sometimes, as if I never did the survey at all, it simply points me back to the main survey selection page after I completely finish one. Not at all is a notice stating "sorry, the advertiser rejected you" or "Survey completed". Like the entire thing never happened. I reached the end screen and know the survey was conducted; but, when I return to Prime, credit is absent, error is not evident, nothing to point to. Though that doesn't happen every time, frequently enough it irritates me and causes me to doubt whether it is worth my time. I really wish they would at least present a note outlining what happened rather than leaving it so vague.