I bought a board/CPU combo over on [H] late last year and couldn't get it to POST. Spent 3 days trying different things - cleared CMOS by jumpering pins, 4 different sticks of RAM, different PSUs, a different CPU. Seller assured me it worked, so I wasn't giving up until I had exhausted all possible fixes.
I had all but given up when I popped out the CMOS battery AND reset the CLR-CMOS - I had never had to do both before, it was usually one or the other - and that did the trick. Something he had left configured in the BIOS didn't agree with my setup on my end. You simply cannot assure the buyer has any competency in fixing an error such as what I ran into, but you have little recourse on the matter as a seller now.
Also, this time of year, static is absolutely horrible here in the Northeast climate, and I make doubly sure to ground myself by touching something metal near my workbench, as a shock can easily kill any component I pick up. If the buyer is located in the NE, I'd guess that he killed his new board/CPU combo by giving it a nice zap as he unboxed or handled it.
Edit: 88, you are in Hanover ?? Dude, sell me some stuff rather than deal with Ebay !!