RDIMM for T3620

Hello.

Im using T3620(xeon e3-1240 v5). I buy Samsung 8G RAM 2133Mhz(ECC) in market.

the RAM was not working with my T3620. just power LED is blinking. and no beep sound.

in the manual, i found that T3620 support ECC. but my T3620 is working witn non-ECC.

is there any reason for this?