ASUS X99-AII / Intel i7-6800K - not working

I'm selling the motherboard of my PC because I can no longer get it to work. After all the tests I performed, it's probably due to the processor (which can be replaced). I cannot guarantee that it is actually the processor. The motherboard is the Asus X99-AII and the chip is the Intel i7-6800K. Both were purchased in the winter of 2016/2017. This is a private sale, so returns and warranty are excluded.