I recently RMA'd an X299 Dark and the replacement board is showing the same behavior as the original. I have not memory installed, just the processor and cooler. 
 
There are two red LEDs that illuminate red instead of white - the #20 5V power which is red and I believe is normal. The other red LED is the  #20 FIVR. I've swapped between a 1600T2 and 1600P2 power supply, replaced all of the PSU cables, replaced the cooler for another AIO unit, and EVGA has replaced the motherboard. I tried removing the processor and powering on the board and there's no post code, but the red FIVR led does go away with no CPU. I can't physically see anything wrong with the CPU and all of the pins in the socket look good. 
 

Yes, with the first board and the second board. When I first got the RMA board back, I powered it on without the CPU to see if I'd get a post code and I didn't. I thought I'd get a C or 00 without a CPU installed. With the CPU installed, the FIVR_LED lights up.

Thanks. For a complete/successful post with no errors codes, yes memory and a GPU are required. It's just strange there's no post error codes with or without a CPU. No change with memory and GPU installed either. Leaning towards something wrong with the processor, but I'd think the board would indicate something wrong with the CPU - unless maybe there's something wrong with the processor's onboard FIVR. I think Broadwell-E and Skylake-X have some of the FIVR components on-board the processor?
 
I've read that the early bios releases for Skylake-X had some issues due to the compatibility with the i5/i7 variants to support both the gaming and HEDT platforms on X299. Is there a way to tell what the shipped bios version is without being able to post to the BIOS menu? I looked on the board, but I don't see any of the stickers or tags that indicate the shipped bios version. 
 
 

I had quite similar issue with an i7-7820X delidded. First boot ok, with the 4 digits display showing codes. On the monitor display the circling dots of Windows 10 and after a while they froze.
Trying everything I use usually to recover the boot of system, no way; I had always FIVR micro led light in white, but with the red one lit at 30% of its normal light.
Changed cpu with a i7-7800X, immediately the codes on 4 digits display and boot of OS went till login window: PC is then working perfectly.

Why the hell People are expecting a Post code without CPU and Memory or Graphics Card install, even if the Board is design for posting a code without anything install or attach to it? Every Board I have had installed in past, first minimal thing is to install CPU, Memory and Graphics Card outside of the Case then Pwr on to test if it's going to Post.

bcavnaugh
@PINKTULIP
Who Knows, same about People not knowing about Intel Chipset Software and Chipsets.
But also EVGA RMA'ed the Motherboard over this, there is more to this.

Thanks TIN. I did in fact get two new i9 7900X last night and the board fired right up. I suspect it was a faulty FIVR or other component on the processor that was the problem. I appreciate EVGA's help and sending me out a replacement even though the CPU was the problem and not the motherboard.
 
Previously, I'd tried the other bios positions and cleaning the pads with isopropyl alcohol and alcohol cleaning pads. It looked like all of the pads on the CPU had slight indentations and the pins were in good contact. I'm guessing something else might have cooked in the chip. 
 
Got the bios updated to the 1.12 release and the OC robot is very nice tool. Not to stray too far off topic, but I noticed different characteristics with the two processor samples that I have. One clocked up to 4.9Ghz and the cpu voltage cranked up to 1.38V at 92C and back down to 1.34 for 4.8Ghz preset and topped out at 85C. The second sample cranked up to 4.7Ghz at 1.264V and briefly up to 4.8Ghz at 1.32V,  before dropping back down to 4.7Ghz and reached 95C. Is there a rule of thumb for which of the two samples is the better chip? Is it the lower voltage or lower temperature sample?
 
 

There is no universal rule for CPU sorting, as your goal might be different, but for raw OC second one probably better. :)