Hi,
I had a similar issue on my ASUS ROG Strix B650E-E board. Someone on this forum suggested booting with only one memory dim installed. If it appears to boot, let it be for a few minutes, power it down and add in the 2nd Dimm. Hopefully if it fails to post with one Dimm, then swap to the other Dimm as well, just to rule out it being one suspect Dimm.
The 650W PSU could be related to the issue. If you can source a 850W or better (assuming you have the funds) it will be worth trying.
Also, I've also seen posts from others along the same lines and it turned out to be a faulty 7800X3D. They replaced it and everything worked as expected. So if booting with one Dimm installed didn't work, then I suggest returning the CPU to the store you bought it from for a replacement.
On my experience it is rarely the motherboard and ASRock boards in general are good as far as I know.
Best of luck
Craig