Asus X570 Dram Led Illuminated

I built a pretty high end rig myself and I think I may be a little out of my depths.

I had it running okay for about 3 weeks; I had Windows 10 installed and a number of other apps I was interested in, but I may have gone too far by installing a 22 year old app (MS FS2000) because now it looks like I've had a RAM failure.

It's an AMD build with an Asus X570 mobo which has 4 LEDs indicating system failures and the DRAM LED is now lit when booted and there's no other action. After a full power off I can get into the BIOS, but it shows for only about 10 seconds before quitting automatically.

I plan on getting a local PC repair shop to check my RAM sticks to see if that really is the problem because I suspect it could alternatively be a PSU problem.

I'm not in any hurry to fix it; I'm done pouring money down this rabbit hole and I have another PC to do my business on, but I'm interested in finding out what may have gone wrong.

My build is as follows:

ROG Strix X570-F Gaming
AMD Ryzen 9 5900X
AMD Radeon RX 6900 XT
64 GB Corsair Vengeance LPX
Corsair RX 1000X PSU
2TB 980 Pro M.2 / 1TB 980 Pro M.2
4TB WD Blue HDD
Noctua NH-D15 Heatsink
Noctua NF-S12A Case fan

I'm in Australia where it's been pretty cold so I doubt system temps have been the problem. I have MSI Afterburner installed and I watch GPU & CPU temps closely; I haven't seen anything out of the ordinary there.

Do any of you guys have a suggestion?