Originally Posted by teclado
Nah, sounds like the motherboard is working fine. If you were to RMA the board, they would power it up, find nothing wrong with it (at 2100MHz RAM), and re-sell it at a slight discount as an "open box" item. Then when they send you a new one, you will have the exact same problem. It's just the same old RAM / bios issues that all of us have been experiencing, with some variability of results depending on RAM and motherboard and bios version.
I'm not sure that I've ever been able to get XMP to work with F3 bios. I've had to manually set multiplier, RAM voltage, and timings.
Here's what I would do if I were you. Go into bios (you can keep f2 for now), disable XMP, set RAM multiplier to 32, set timings to manual, set DRAM voltage to whatever your RAM is rated for (probably 1.35V), set timings to whatever it says on the side of your RAM sticks. See if that boots at 3200MHz. If not, try 2933MHz (lower the multiplier). You can also try F3 bios with manual RAM settings. It's possible that your RAM just will not work at 3200MHz right now (which I think a number of people were reporting only being able to get 2933MHz to work with the Flare X memory). It's irritating, but you might have to wait for a bios update to get 3200MHz RAM.
Alternatively, you could maybe return the RAM and get this kit: https://www.amazon.com/gp/product/B0143UM4TC/ref=od_aui_detailpages02?ie=UTF8&psc=1
I'm using that kit with the K7 motherboard, F3 bios, and I've had no issues getting 3200MHz when manually setting RAM multi, timings, and voltage =1.35V. I'm running a 1600X and I honestly have no idea if different processors matter (your 1800X vs my 1600X). I wouldn't expect that, but I can't say definitively because there is a massive knowledge hole regarding the inner workings of Ryzen.