Matrix owes me a I7 CPU

I brought a fully functioning pc to them, all components were a day old, yet despite a minor issue, when i returned they had somehow managed to get the cpu not to post, the pc would not even boot anymore. Their "technicians" claimed not to understand what happened or what could be the problem but i personally booted it in store in front of them, so it was working. The cpu was a i7 14700KF, its quite an expensive cpu, and despite all this they are not going to replace the component, i hope that i can get the seller to replace it.