asher6, what do you have installed in the Z240 now? Did you take out all the 8GB memory DIMMs, and install the 16GB DIMM by itself? Or are you putting in the 16GB DIMM and still have other memory DIMMs installed?
If you have not done this already, take out all the memory DIMMs and install only the 16GB DIMM in black slot farthest away from the CPU. Does the system boot with only this DIMM?