Survey Sampling International Survey Spot; Opinion Outpost Finish survey; then told I don't qualify Nationwide

I have been a member of both Survey Spot and Opinion Outpost for some months.  Both are run by Survey Sampling International.  I also am a member of the Harris Poll surveys and Ipsos International.  I was a member of PCH surveys for many years before they shut it down.

Only those run by SSI sometimes seem to be ripoff artistss.  to be fair, I have on several occasions been able to get points for completing surveys, and have even been able to redeem them a few times.  But more often than not, I complete a survey, sometimes a long and complicated one, only to get a message that I don't qualify (after having qualifed in the preliminary questioning), or that for some other reason my answers can't be recorded or accepted.  I think they just don't want to pay their panelists.

I have never had this problem with Harris or Ipsos.