Try blowing air in through the petcock hole to see if the air comes out the filler cap??
edit;
Maybe there is a "Dam" of tank sealer in front of the hole keeping the fuel from reaching the hole. Put the gas cap on and tip the front of the tank up(carefully)to see if any gas comes out.
edit;
Maybe there is a "Dam" of tank sealer in front of the hole keeping the fuel from reaching the hole. Put the gas cap on and tip the front of the tank up(carefully)to see if any gas comes out.