Just wanted to say that about a month and a half ago I started using Priceline NYOP to get a rental car in Vegas for 8/26-8/29, and it was working at the time, but I considered the rates too high at that point($131). Then about 3 weeks ago I started getting the same message as you. this continued on until last week when I tried doing NYOP for every week thru January, I still got the same message. I then contacted Priceline corporate and they towed the company line there and wouldn't answer my question as to why NYOP was not available in Vegas for the next 6 months, they just said that its the rental car companies that make vehicles available and unavailable. They attempted to calm me by giving me a 10% discount code on a PRICELINE EXPRESS rental. I don't understand why these rates are so ridiculous, fees add on approximately 60-80% of the total cost of the rental, so currently my 10% coupon is only good for an $8.40 discount bringing the total down to $133.XX. this is an exorbitant amount considering that I rented a car in Vegas through carrentals.com for $66.07 in 2015 for the same exact dates..