Reading the FAQ they state upfront that they will source tires from many tire sellers and are not able to select the tires you receive by DOT dates and that, as you said, they will ship tires up to 4 years old. And, if you get a tire older than that they will pay the shipping back to them.
They also state that once mounted no tire is returnable.
So, this begs the question... why did you buy tires from them? They didn't hide any of this info.
2017 Winnebago Adventurer 37F
2016 Lincoln MKX Toad