They wouldn't refund my money without a receipt

Last year during the annual clearance sale, my husband and I bought a brand new HVAC unit for the living room.

The HVAC unit has heat and AC.

I never had the chance to use the new HVAC unit, so the first time we hooked it up and turned it on was about 6 months after we made the clearance sale purchase. I expected no problems with the setup, and it was a breeze. The biggest problem was the fact that the machine would not turn on when we hooked up the power. I checked the breaker and the fuse box. I didn’t see anything that would cause a problem. We tried another outlet and the problem seemed to be the HVAC unit. I told my wife that we were going to need to take the machine back to the hardware store. I asked her if she remembered where the receipt was placed after we bought the AC unit. She did not even remember keeping the receipt. I was hoping that the store would have a copy of our receipt on file. I took the HVAC machine to the store and they were not going to return it without a receipt. Even after they found the order under my debit card, they still refused to refund my money because I did not have the original receipt from the sale. The best they could do was offer me store credit to purchase something else. I was easily quite frustrated with the entire situation, but I did not believe there was anything I could do.
Cooling and heating company