I also tried to get pit tickets for this show as soon as they went on sale but it said none were available. I ended up getting floor seats though. Went back a couple hours later to try the radio code and pit tickets were available with that, but I didn't get those since I already bought the others.
Go to the link below and click REQUEST MEET & GREET to enter the lottery.
You could try to purchase pit tickets when the public onsale happens as there may have only been some of the pit tickets allotted for presale and others being held for the public onsale.