It worked fine in windows. Maybe update the BIOS with the older working CPU. Reseat RAM, clear BIOS, maybe remove battery from motherboard with it unplugged from the wall. let it sit for a while. Tap power button to help drain builtup power in the system. Then replace the battery and plug it back in and power it on. It should recognize the CPU.
It's hard to damage the CPU, but not impossible. Check the CPU socket in the light and look for bent or misaligned pins.