new pc fails to power up

Case: Phanteks Enthoo
MB: ASUS ATX H770-Plus D4
CPU: i3 -12100F LGA1700
RAM: 2 x 16GB DDR4
PSU: Red Dragon 850W RGB modular

Unfortunately, after installing all of the above with a 2TB Seagate SATA HD, the computer fails to show any signs of life.

The PSU has a test plug that when plugged into the PSU and the PSU energized the unit's fan and lights come on, so I guess the PSU is supposedly working.

Unfortunately the PSU did not come with a manual and I couldn't find one online, but the hookup looked fairly simple:
- connect 18/6 pin connector on back of PSU and other 24 pin end to ATX power port
- connect 8 pin cpu cable to cpu port on PSU and 12V CPU port on MB
- sata power cable from HD to PSU sata port, and sata data cable from HD to sata1 port on MB

I have double checked CPU triangle on CPU is oriented toward little triangle om MB and the CPU sits snuggly in the socket before clamping it down. CPU fan was a bit of a PITA to get all 4 posts snugged down tight. I think they are, but I cannot imagine that causing me any power up issues in any event.

I also pulled the cmos battery for a minute or so to clear anything that could have possibly been holding up the power up.

Other than that, I wonder if anyone has any suggs or advice before I reach out to the vendor? Thks.

You're trying to turn on the PC with the power button on the case? Did you double-check that you connected the bunch of front-Panel cables (especially the PowerSwitch) correctly, following the manual or the printed labels on the motherboard (next to the fPanel jumpers)? You can also short the 2 PowerSwitch Pins with a metal screwdriver to make sure it's not the Case that's giving you trouble.

The PSU connections you list sound about right. Do you see any sort of LED lit on your motherboard?