I'm having some issues with a new RAM stick

I recently bought a new 8Gb ddr3 SO-DIMM ram stick to replace my 2Gb Ram stick, my laptop ships with 6Gbs of memory intalled, a 2Gb stick and a 4Gb stick, it is advertized as upgradeable, I changed the 2 Gb stick for the 8Gb stick and immediately went to the BIOS, it only read 4Gb of memory, I then checked both RAM slots, using the 2Gb, 4Gb and 8Gb in each slot and in every combination, the slots seemed to be fine, and the coputer always read the 2 old sticks, but never detected the new one,...

I'm having some issues with a new RAM stick