ECC RAM needs a compatible motherboard and CPU.

You can’t just swap it in. Most consumer motherboards and CPUs (Intel Core, AMD Ryzen non-Pro) don’t support ECC at all, or they silently run it in non-ECC mode.

ECC RAM is designed for servers and workstations. The memory controller on the CPU has to support it, and the motherboard BIOS has to be wired to handle it. On Intel, you usually need a Xeon or Core i3 (oddly) plus a C-series chipset motherboard. On AMD, Ryzen Pro or Threadripper with a workstation board works, but standard Ryzen is hit-or-miss — sometimes it boots, sometimes it ignores ECC entirely.

Check your motherboard QVL (qualified vendor list) and CPU specs before buying. If your current setup isn’t already ECC-capable, the upgrade will cost you a new motherboard and possibly a new CPU.

This is not a “buy two sticks and you’re done” situation.