Use the known "working RAM sticks" and move them to the other two slots. If they are currently present in 2 and 4, move them to 1 and 3. See if they work there. If they do, take the RAM sticks you just received and insert them into slots 2 and 4. If the system boots, then move them to slots 1 and 3. Let's see if you have a bad RAM slot on the motherboard. I'm leaning on a potential voltage incompatibility. Alienware RAM typically runs stock at 1.2v whereas 3rd party RAM runs [NAME].35v and that could be the problem that the motherboard doesn't agree with now that there are 4 of them. We'll have a better picture working with just 2 sticks of RAM and trying them each in slots 2 and 4 and then in 1 and 3. Just make sure you know which sticks are the ones you just received.
I have an Alienware Aurora R12 with an i7-11700k.  I was using 32GB of corsair vengeance 3200mhz 16x2) and I went to add another 2 more sticks, and pc went into a boot cycle several times before finally informing me memory has changed. I enter bios and its reading all 4 sticks buy at 2133 I enable xmp and the pc wont load. I get the orange light blinking before it reboots itself. It does this several times before loading in with xmp disabled. Runs fine as is but id like to know how to get my speeds 
Aurora R12, XMP causing pc to not load