Why do identical sticks of RAM refuse to work with each other?

Question

Iron

Hello. I have an MSI GX660 laptop, I bought it in 2011 (notebook specifications are here ). It has RAM: Kingston KVR1333D3S9 / 4G 4GB 2Rx8 512M x 64-Bit PC3-10600 CL9 204-Pin SODIMM , I bought the same RAM with the same characteristics, in the BIOS you can see that it has become 8 GB, but when I turn on the laptop it will work a little , a few minutes and a blue screen error pops up.
What is the problem, how to make both RAMs work together?
The laptop has Windows 10 installed.

Answer 1

Run MemTest86+ from the flash drive.
Possibly the second bar is broken.