Documenting my woes here, just in case someone else is faced with the same issue. There is one other (very long) thread about a somewhat similar experience, I will keep this dry, technical, and focused on process.
Got my DIY 16, with 64GB Ram and 1TB WD Black also provided by Frame.Work. Everything assembled as per instructions, all contacts fully seated, used an electrostatic mat and grounding bracelet while doing so. On first boot, with midplate closed and inputs installed, no image on screen, no sound from fans. After some sleuthing, left it on for an hour, in case RAM needed to be ātrainedā, nothing happened.
Took everything out, tried one dimm at a time in either bank. After several tries eventually got to boot with only one dimm on bank 1. Got all the way to BIOS, tried to boot from install USB (verified working in both UEFI and legacy modes in a different machine), BIOS would recognize stick was connected but not be able to boot from it.
Went back in, tried swapping dimm on known working bank, no go. Went back to known working dimm, no go. Now I get the power on button blinking (4 secs on, 1 sec off). Contacted support, within five hours they provided me a procedure to reset the mainboard state: with machine connected to AC power, press the intrusion switch 10 times, for 2 seconds each time. Then power on and record video of debug code lights. The result of this was that on the first 12 blinks I get green on everything except blink 6 (touchpad, which makes sense, as midplate is not installed at this point), and then on the final 8 blinks I get 1 blue, 7 green (code 0x80, basic memory test). No screen, power button shows same behavior, fans donāt move. Communicated results to support, waiting to hear back from them.
A few notes: the one time I made it to the BIOS, memory test showed everything was a-ok. I was able to reboot a few times and output detailed info. In the current state, when you plug in to AC, board lights blink red (warning, donāt disconnect anything). However, when you go through the 10 presses eventually they alternate to red/blue. I say eventually because the behavior is not consistent, sometimes 5th press, sometimes later. Finally, just repeated reset procedure and now I get red blinks at positions 6, 7, 8. See here for meaning of basic post lights and bit values for post code section (final 8 blinks).
Hope this helps anyone seeing the same behavior, will update here as I hear back from support. They seem responsive, escalated to L2 fairly quickly when FedEx missed delivering my package and did not contact me to reschedule (not in the US, procedures in this country are different).