New Build Won't Turn On--and when it does I get the line through the circle error

I've been having two problems with the build. I have no idea if they're related to one another or not.

First the gear:
GIGABYTE Z390 AORUS PRO
Sapphire 11265-05-20G Radeon Pulse RX 580
Intel Core i9-9900K Coffee Lake 8-Core
Corsair 850+ PSU
Crucial Ballistix Tactical 64 GB Kit 4x 16 GB DDR4 3000 MHz
3 x 3gb WD HD's
2 x 2gb Samsung SSD's
1 x 512mb M.2
inside a Corsair 300R case.

Issue 1: Computer will not turn on. It will click, sometimes once, sometimes twice. I have disconnected everything, reset the CMOS, plugged everything back in (although I now have removed all PCI expansion cards [Thunderbolt and wifi]) except the Sapphire, and sometimes the computer will start up and allow me to input BIOS settings and start the installation process. However, if/when that happens, I run into Issue 2.

Issue 2: I make it about halfway through the installation process (finish with the bios, finish with formatting the M.2, prepare for Mojave installation) when the apple sign turns into a circle with a line through it. Shortly after this happens (sometimes I can restart once or twice), Issue 1 begins again and I have to start from scratch!

Is this a CPU power issue? A bad cord somewhere that needs to be replaced? Or am I missing something obvious (most likely)?

Thanks in advance!