Your motherboard probably doesn't support ECC.

Probably not, unless it’s a proper workstation or server board. Consumer motherboards (even ones that technically “support” ECC) often only allow it with specific CPUs and may not actually do error correction – they’ll just boot with the sticks installed.

Go to the motherboard manufacturer’s website, find your exact model, and look at the memory specification page. If it says “ECC support” or “unbuffered ECC” you might be in luck. But also check the CPU support list – the CPU’s memory controller has to support ECC too. On AMD, most Ryzen chips support unbuffered ECC. On Intel, you usually need a Xeon or certain Core i5/i7 (non-K) chips on select chipsets like W680 or C series.

The easiest way: look at the memory QVL (Qualified Vendor List) for the board. If they list ECC modules, it’s officially tested. If not, you’re gambling.

Don’t assume because the slots fit. ECC and non-ECC look identical in a consumer board. The difference is in the chipset and CPU support.