It's trying to initialize the CPU/DRAM and failing. Probably wouldn't be getting that far if your 8 pin CPU power wasn't connected. Very possible it's DRAM related. I'd test with 1 stick of RAM installed. Clear CMOS if it fails and try once again. What CPU?
That's a pretty new CPU. You need BIOS F62 as a minimum: https://www.gigabyte.com/Motherboard/B450-AORUS-PRO-WIFI-rev-1x/support#support-cpu
That's most likely you're issue. Lights are telling you that it initializes the CPU and then goes to RAM and loops. Most likely that means it's dying initializing the onboard memory controller. You're going to need an older Ryzen processor to flash the BIOS with. I don't see any flashback feature on that board to flash without a CPU unfortunately.
You need a CPU old enough to POST so that you can flash the BIOS. The BIOS' that support this CPU are all from January/February. Even if you get a newer board like a B550, it's a luck of the draw. The store does offer a service to update the BIOS for you.
The CPU seems to be the problem. It's an older architecture(Renoir - Zen 2), but they've changed something that I'm assuming requires a micro code update. If you're looking to change a component, I'd swap the CPU for a Zen 3. Maybe a 5600X or 5600G.
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