How can I have a commission-less sale?

I have an advertiser on CJ that I have gotten commissions from before. But sometimes I get a "lead" or "sale" (I've had both) but no commission.

I have found CJ's website very difficult to get basic info from so I am only guessing about what lead and sale even mean to them.

But how can they sometimes pay and sometimes not?? A sale means I get a commission, right? Is there something I'm missing here? (Besides my $15

I've gotten commissions from both "leads" and "sales" in the past too. What gives?

 

Have you tried asking CJ about it? They will be able to give you a more specific answer I expect.