Why aren't these 2 RAM working together in my HP Pavilion G6 2009 Tx

[IAmShivam]

I bought a new Hynix 4 GB 1Rx8 PC3L 12800-11-12-B4 (HMT451S6AFR8A) RAM for my HP Pavilion G6 2009 Tx. (https://www.amazon.in/Hynix-Hmt451S6Afr8A-Pb-Pc3-12800-Ddr3-1600Mhz-Unbuffered/dp/B00FKEZ218)

My laptop came with 2GB variant of this HP 641369-001 4GB 1600Mhz PC3-12800 memory module

(https://www.amazon.com/HP-641369-001-1600Mhz-PC3-12800-memory/dp/B008L325TW)

I tried plugging both of them together but they aren't working. The system is just not switching on. 

Both of them work individually but it isn't booting together. 

I'm tried interchanging slots and releasing static. I know that new RAM is low voltage type but I read that PC3L one can function along with PC3.

Can anybody explain why is this happening even though specifications for both RAMS are compatible?

Can I somehow make them work together to get a total of 6GB Ram? 

[iomare]

Hi,

There is probably a compatibility issue between the two RAMs. Does the 4GB stick work in each slot? If yes, I would purchase another 4GB stick of the same RAM.

Regards,

David

[IAmShivam]

Yes, it does work in both the slots. Don't wanna buy another one that's why trying to solve the compatibility issue if there is any. I see no apparent reason for incompatibility though. 

[iomare]

Well sometimes it just happens with two different RAMs especially if one is DDR3L and the other DDR3.

Regards,

David