Brand new XPS 8900 Win 10 won't turn on, power light blinks in yellow 2 times pauses 7 times pauses then repeats.

I haven't seen a chart explaining the power button blink codes on the XPS 8900. And there's nothing in the manual.

You should contact Dell tech support immediately. You have 21 days from invoice date (not delivery date) to have them take it back. And then you can order another one.

Otherwise, tech support should work with you to solve the problem under the warranty on this system.

If you're comfortable working inside the case, it's possible something got jarred out of place during shipment. So you can try reseating the RAM modules and PCI-e cards, and cables between motherboard and drives, and to power supply etc. Be sure to read the instructions about working inside your PC in the manual before you open the case.

I disconnected from the wall, pushed the power button a few times to discharge the system, then opened it up and removed the CMOS battery. Then re-seated the power connectors and RAM. I waited 30 mins, then reinserted the CMOS battery and that fixed it.