It could be the RAM is damaged (either via your handling, or the guy who sent it to you).
RAM is super sensitive to static discharge so much so that the slightest amount of static buildup in your body can render the RAM useless if you touch it. I've know alot of friends who have tried to upgrade their own ram and fried the RAM they bought by handling it incorrectly. Even proffessionals will mess up from time to time even when installing it properly (with the anti static wrist band attached, etc)
Another possibility is you don't have the RAM set up properly in the bios, this sounds like a good possibility as that would render all the RAM unusable by the computer (but it may still be able to count it, just not access it)
Also what TDK said
