Here is your motherboard's memory specifications...
Number of Memory Slots
Maximum Memory Supported
The only thing I can think of off the top of my head is maybe your RAM isn't 1333MHz. Post your RAM Model and I'll look at its specs.
Yeah well that's true my mobo support 1333Mhz or 2000Mhz Those sticks are indeed 1600Mhz.
But i had the change to just auto config my memory in the bios en he automaticly downgrade it to 1333MHz and i have the setting extreme profile 1 so the automatic are set to 1600MHz. But nothing works..
Try plugging your RAM modules into different slots. And even different combinations.
Try and plug in each module individually and see if the system can bootup and recognize the full 4gb from each stick.
I feel it has been said but seriously read the manual carefully. Sometimes they are very very specific for memory best practices. Perhaps the RAM brand is not recommended for the motherboard. Unlikely but still possible.