No sign of life new build HELP!

I’ll cut straight to the details, new build not powering on at all, no LEDs lighting up on mobo… specs for new and old build at bottom.

What i’ve Tried:

check PSU cables were fully connected

checked for any potential grounding issues or shorts

checked new Mobo for potentially damaged components

New PSU passes paper clip test

Took out new GPU

Re-seated new CPU

Reseated new RAM

Tried connecting old PSU to new mobo but still no sign of life

Tried connecting new PSU to old build, won’t boot but the power LED starts blinking (the built in RGB on old mobo doesn’t turn on tho)

Connected old PSU to old build just to be sure it still worked and lo behold it booted no issue

New build:

Asrock b850 livemixer Ryzen 9 7900x 16gb DDR5 patriot viper elite 5 (6000) Asrock 9070xt Asrock steel legend 850 watt t-force gc pro m.2 (hyper m.2 slot) samsung 970evo (bottom left m.2 slot) Cooler master 360 elite AIO

Old build: (in its current test-bench state)

Asus prime z390-a core i7 9700k corsair vengeance 8gb ddr4 PowerSpec 750 watt cooler master 212 air cooler