OptiPlex 9010

I have an OptiPlex 9010 desktop computer
 Core i7 3770 @ 3.40GHz
Motherboard: 0M9KCM
DDR3 798MHz (11-11-11-28) 16 GB (4 * 4GB)
Windows 8 Pro 64-bit
The problem does not appear in BIOS except 8GB
 means 2 SLOT is active and 2 is not active (empty), all SLOTS works when tested with 2 RAM only . when 4 RAM only 2 SLOT
All RAMS work in another device.
the system information in Windows 8GB only.
  BIOS updated to update (A30), BIOS rest same result 8GB only.
I tried another Windows system (Windows 10) on the same motherboard the same result.
For system information display programs such as CPUID (CPU-Z) or Speccy, 16 GB is displayed
I did not know why you tried all the options did not change the result
I hope you help me. Greetings