Payout dropping to zero on day of payout...Why????

Hi all, any info would be greatly appreciated.

I'm pretty new here and rarely post anything that gets more than a cent or two so this post isn't so much about me being worried about my "2 cents" (pun intended) than it is about me being confused as heck about how and why this keep happening. I have had a number of posts now that have had an estimated payout of 3 or 4 cents which has stayed at 3 or 4 cents for the entire week and right on the day it is supposed to pay out, the estimated payout drops to zero and I get nothing...Can anybody tell me how or why this happens and perhaps how best to prevent it in the future?