[SOLVED] MSI X470 Gaming Plus - Black Screen and CPU Debug Light On

[drivesafe]

Hello, it's the first time building a computer; here is the build: https://pcpartpicker.com/list/QnYtYH.

Currently:
After powering on, LED's and fans run. Keyboard lights up. But no display output. CPU Debug light is on.

Initially:
-I installed parts as instructed by research/manuals. X470 Gaming Plus MOBO has "Ryzen 3000 Ready" sticker on the box.
-Initially this problem occurred, I reseated RAM and CPU heatsink- was able to get into BIOS and I installed Windows 10 Home on either the SSD or HDD (unsure).
-Reboot to finish installing
-Assumed reboot was stuck after nothing happened after 10 minutes of computer running with black screen. Keyboard LED was off. Powered down by holding power button.
-Now, CPU Debug light is on and I get no display.

I have tried:
-Reseating CPU and heatsink
-Reseating RAM
-Reseating GPU
-Replugging 24pin and 8pin power connectors
-CMOS Reset Button
-Removing CMOS Battery
-Switching display output between GPU and Mobo

I'm now thinking it might be due to an unstable BIOS. I did request a boot kit from AMD.
Any help would be very appreciated, as I am pretty frustrated after 5-ish hours of troubleshooting. Thank you.

 

[Calvin7]

Only plugged in some of the power connectors, not all three:

• 1 x 24-pin ATX main power connector
• 1 x 8-pin ATX 12V power connector
• 1 x 4-pin ATX 12V power connector

Power supply does not have proper connectors:
Features
Connectors1 x 24-pin ATX
1 x EPS Connector
1 x Floppy Connector
4 x 4-Pin Peripheral Connector
4 x PCIe Connector
6 x SATA Connector

 

[drivesafe]

Only plugged in some of the power connectors, not all three:

• 1 x 24-pin ATX main power connector
• 1 x 8-pin ATX 12V power connector
• 1 x 4-pin ATX 12V power connector

Power supply does not have proper connectors:
Features
Connectors1 x 24-pin ATX
1 x EPS Connector
1 x Floppy Connector
4 x 4-Pin Peripheral Connector
4 x PCIe Connector
6 x SATA Connector

Oh <Mod Edit>, you're totally right... Thank you....
There's no way to go about this other than to buy a new PSU, huh?
Or am I able to buy a modular cable for the ATX 4pin?