Pay on receipt Autoinvoice does not pull receipt and does not run invoice open interface

 Hi , I create a po and received successfully against that po for a supplier who is
set up as Pay site, Primary Pay has been set,
pay on receipt is set in self billing region.
invoice summary level is set as receipt or pay site.

And when I run the pay on receipt autoinvoice , it does not pull the receipt and hence it not running the payable open invoice interface and hence no invoice is created.
Is there any setup that I am missing. I checked all the setups,they seem to be fine. What is that I am missing here.