Question Ram stick not recognized- Lenovo N500 laptop

[avz3]

I have an old Lenovo N500 laptop. it comes with a 2Gb ram. I wanted to increase the memory to 4Gb with a 2Gb ram stick. I've inserted it but unfortunately it's not recognized by the laptop. the original ram stick is : 40Y8404 and from what I've found it's chip description (from DMS website) is: 2GB, 667MHz, DDR2-667 PC2-5300, 200p SODIMM, 1.8v the stick that I wanted to install is marked: DDR2-667MHz PC2-5300 1.8V would like to have your advise.