Poweredge t20 registered memory query

Hi,

I have recently purchased a T20 tower as my first foray into the world of home servers (non Xeon model).  I was under the impression that these systems supported ECC registered memory, but when I try to populate the board with 4x Hynix 4GB ECC DIMMS (1333Mhz) the board does not recognise them (No memory POST code). 

The part number of this memory is HMT151R7TFR4C-H9 & the spec page is here https://www.skhynix.com/eolproducts.view.do?pronm=DDR3+SDRAM&srnm=HMT151R7TFR4C&rk=20&rc=module

is it possible to use this memory, or am I wasting my time attempting to get it running?

Thank you in advance for any advice & assistance :)