Predator 9000 kw generator trash

I bought this generator from Harbor Freight, and it didn't even work.
I got charged a 20% restocking fee because the box was opened. They had 6 of these generators returned that day. The girl behind the counter told me, and they wanted me to exchange it out for another one. Why would I exchange it out for another one that doesn't work or will I fail soon? I borrowed a friend's 3500 kw generator, and it did the job just fine. Harbor Freight has refused to give me a full refund. I called customer service and talked to the store manager. I did buy stuff from them all the time, so that 20% they cost me, they lost out more than that by losing me as a customer, and I hope other people seeing this refuse to use them also.