Hello, and thank you for posting your question in our forum. There are several possible reasons for this problem:
- Outdated motherboard BIOS. Make sure you're using the latest firmware.
- Defective motherboard. Everything else can work just fine, but the motherboard could have a defect.
- Incompatible memory modules. Refer to the manual for DIMM ordering and placement.
There is still a lot of data you'll need to share. For example, what Operating System are you using? If it's Windows 7 64-bit, what does it say beside "Installed Memory (RAM)" when you right-click on 'Computer' and choose properties? You'll know there's an issue with the motherboard if it shows 12GB installed. How much memory does the BIOS report during POST?