You'll need to flip a BIOS setting for ECC RAM.

Yes. On the Asus Pro WS X570-Ace, ECC is not enabled by default. You have to go into the BIOS and turn it on.

Most consumer boards that support ECC keep it disabled out of the box, even the “Pro” models. The Asus X570 is no different. After you install your ECC UDIMMs, boot into the BIOS, head to Advanced → AMD CBS → UMC Common Options → ECC Configuration, and set ECC Mode to Enabled. Save and reboot.

One thing to watch: this board only supports unbuffered ECC (UDIMMs), not registered or load-reduced. Double-check your RAM kit says “ECC UDIMM” or “ECC unbuffered” before buying. If you slap in non-ECC sticks, the setting does nothing.

Don’t skip this step, or you’ll just have expensive non-ECC RAM.