you might have already checked this, I know it seems to be obvious, but it bit me last time too: make sure to check that it doesn't want a specific ram slot order, it'll say in the manual.

(and if you have a recently-released CPU, you might need a firmware update on the motherboard, which I think was the source of my RAM errors two motherboards ago (it had other problems tho))

I actually just had this exact problem with this exact motherboard and CPU. Apparently the x570-plus has a lot of stock from early 2020 that’s still being sold and this series of ryzen came out in late 2020– I know you said that you think yours is compatible with ryzen 5000 series, but I bought a brand new motherboard and it had a 3-year-old bios on it! You can see the BIOS version that came out of the factory on the motherboard, it’s the last 4 digits of the number printed on the barcode next to the CPU slot

this page shows what version is required for each ryzen version: https://www.asus.com/motherboards-components/motherboards/tuf-gaming/tuf-gaming-x570-plus/helpdesk_cpu/?model2Name=TUF-GAMING-X570-PLUS

just… double-check, because I drove myself crazy over this in january and once I found out it was that, I called around to repair shops in the area until I found one that had a stock of older ryzen chips lying around. It took him 30 minutes and he charged me $60 to update the BIOS and get me on my way, and things have been working great ever since.