@Tesla1856Thanks, for the response I was typing up my solution as you responded.

SOLVED:

Ended up figuring this out myself.

I tested in slots 3,4 and all other combinations of slots and it didn't work.

Then I booted with one stick and got the 'amount of memory has changed' prompt to which I hit okay. I suspected that okay needed to be hit on this screen in order to again change the amount of RAM or it would be reported as an error.

I shut down and installed the second stick in slot 2 and it powered up and worked! The tech they had sent me was a contractor who deals with a variety of machines so I don't think he fully understood this system (understandably). I am pretty certain that the technician ended up either booting into bios or powering down instead of hitting 'okay' before installing the second stick. The original two stick configuration probably failed because the motherboard was expecting only a single stick.

So solution:
-Boot up with only one stick installed in slot 1 (the first white slot).
-It will take longer to boot after changing memory.
-Press okay on the 'memory has changed screen'
-Allow it to boot to windows, you don't need to sign in and can power off using the button on the bottom right of the screen.
-Power down (make sure to de-flea or at least tap the PSU with your hands) and add the stick to slot 2 or other slots if you have more RAM.
-Boot, wait, and press okay again on the 'memory has changed screen'. If you get error lights again you may need to start again from the beginning.

Some Aurora manuals have been incorrect on ram slots over the years (personally, I know the R6 and R7 PDFs were back then).

Anyway, it's simple.

Obviously, ALL INSTALLED DIMMs must be 100% compatible with the motherboard (no exceptions to this rule).

There are TWO MEMORY-BANKS in all these Intel-based Auroras (R5 to whatever).

Each MEMORY-BANK is comprised of 2 DIMM-slots. They both have the same color for their hold-down-clips (ie, White).

A pair of EXACTLY-MATCHING DIMMs should be placed in each MEMORY-BANK. They should run in Dual-Channel.

Conceivably, slightly mis-matched DIMMs can be used, but only ONE-DIMM in each MEMORY-BANK. They will not run Dual-Channel. For this and other reasons, it's just not recommended.

CPUID's CPU-Z is good.
Passmark's MemTest86 is very helpful.

Good work.

So, the replacement Aurora-R11 motherboard is working properly (best you can tell), and you are satisfied now that your favorite ram is working?

@Tesla1856 
Well, not exactly.

I thought I had it figured out but something is definitely wrong, it may be just software but I'm afraid the tech might have been correct in ordering a replacement. This is so incredibly frustrating.

The RAM will work in 1 and 2 properly after the steps above. As per RAM speed test applications it is running properly and in dual channel mode. However, as soon as I reset I get the error code 4 for bad RAM. I can get both to work again if I reset with one and repeat the steps above again but this has to be done every time I turn the PC on and off.

I'm going to try a few things and see if I can get it to work. Either way this is pretty concerning, this did not happen with the last board at all. It booted correctly until it failed.

Thank you! That worked and I didn't need to reset the CMOS. It now resets without an error code.

I am a little confused though, they were in slots 1 and 2. I thought 3 and 4 were xmp?

Yea the xmp profiles are stored on the RAM sticks.  The oem and retail hyperx have different xmp profiles.  You can load the profiles via BIOs, doesn't matter which slot is used 1 2 3 or 4.  Only matched RAM sets should be run in the same colored tabs.  Matched is a kit purchased as a kit.  The ram sticks need to be identical to run together in the same color tab or issues come up.

Also you can't enable xmp  unless all the xmp profiles are the same on all sticks otherwise problems come up too.  The pc can't run ram in one slot at one speed and in another slot at a different speed.

@r72019 
I thought that even mismatched speeds could run in sequential slots? Just curious, I know you know better than I do, what kind of issues?

I have them in 1 and 2 right now so they'll run dual channel, from what I can remember with CPUZ running on 1 and 3 runs in single channel.

Should I just sell / return the RAM and get matching 2666?

So in the above example, I ended up RMA'ing the RAM.  If you're comfortable with it, keep it.  If you have doubts, return it for a matched set.