The computer does not start with new memory modules, what should I do?

Question

RAM

I bought two Zeppelin sticks for 4Gb DDR3 1333MHz. I installed
it, the computer does not start, there is no blue screen, it just does not want to boot, the state is like in sleep mode.
I reset the bios to standard settings, pulled out the battery, put it separately in different slots. everything is useless.
I put one old bar on 2Gb and a new one on 4Gb, the computer started up but did not determine 4Gb, but cpuz sees 4Gb. Shows 6Gb.
On the official website of the motherboard "Support DDR3 1333/1066/800 SDRAM" / 2 x 240-pin DDR3 DIMM sockets with support up to 8 GB
On the official website of the processor "System bus frequency 800 MHz FSB"
As I understand it, the computer does not start because of the incompatibility of the CPU and RAM bus?
Am I understanding correctly or not?