Resolved the issue by removing the original working 8GB under keyboard which then caused the new 8GB installed under the laptop to produce a POST error beep sequence 1 3 3 1 which indictaed a DIMM problem. Re-seated the new memory and it all burst back into life. Re-installed the original 8GB of memory again and lo and behold I now have 16GB of memory.
Odd that the memory would only error during POST without the original memory installed.
My guess is that the 2 sticks under teh laptop was never seatted properly (poor contact, dust...whatever the reason). The post error occurred not because it was complaining about the 2 sticks you left in there, but it was complaining that it didn't detect any. It's not about the memory being "original" or not. It's about those two new sticks were never detected until you reseated them.