I just assembled this system and it has never POSTed. When I first turned it on, it immediately powered off, then powered back on by itself, then off and back on. The CATERR light is red, as are both DIMM indicators.
 
I've tried swapping the DIMMs and tried having just one in each slot. I also see the same thing if I power it on with both DIMMs removed.
 
I've tried all three BIOS switch positions, with no difference.
 
I've tried two different PSUs -- an XFX PRO 1250W and an EVGA Supernova 1000 T2. Same experience.
 
The CPU is an i7-9700K. The RAM is Corsair CMW16GX4M2C3200C14.
 
I don't have a different CPU or RAM on hand to test. What should I try next?

Thank you for the reply.
 
Got everything out onto a test bench with elevated standoffs and made sure all of the power connections were good. Still getting exactly the same result.
 
The GPU is a new EVGA FTW3 2080 Ti. I also tested with a 690 and with no GPU installed. Always the same thing.

I let it run for about 10 minutes. No change.
 
I should have a G.SKILL F4-4266C19D-16GTRS kit to test on Sunday.
 
Thanks for all of the help so far.

Tested with 1 of the G.SKILL DIMMs, but unfortunately I still see the same error lights.
 
Connections and pins all look good to me. CPU looks fine too.

Probably not helpful but I got the 2x red DIMM lights on a cold boot, unplugged the power supply and it started right up. 2 days later cold boot got the CATERR red light. Same unplugged the power supply for a minute, started right up. 2 days later got a death screech and smell of magic smoke from my 6 month old 1000W G3. Not sure if the power supply had anything to do with those 2 errors.