Hi, my name is***** guess you know that a Q-code 55 is "Memory Not Installed," since you said you've reinstalled the memory. Here are a couple of other things to check:
1) Double check the compatibility list to make sure the memory you're using is supported by the motherboard. If you tell me what memory you're using, I can check it also.
2) Make sure the CPU is seated properly and you haven't bent any of the pins or crushed it with your cooler. The memory controller is built in to the CPU and might be affected that way.
3) Take all your add-on cards out and use only one stick of memory in A2. Then try to boot. If that works, next insert the remaining memory sticks and see what happens. If that also works, insert your cards one by one until you find out which one is causing the issue.
4) Upgrade the BIOS to the latest version. You can use the USB BIOS Flashback since you don't have an operating system installed yet. Tech support would probably have you do this, although I doubt it would make any difference personally.
5) If it still doesn't work, I would RMA the motherboard.
This gives you some place to start. Please chat me back and we can discuss it further.