i did do the config as suggested on the board, but only just noticed the the layout.
I slotted the dimms in numerically by suffix serial number correlating to their kit (36, 37, 38, 39/40,41,42,43) and then seated them in according to the alphanumeric slot (A1/36, B1/37, C1/38, D1/39, A2/40, B2/41, C2/42, D2/43).
After attempting this only C1/C2, D1/D2 show as populated.
Any other ideas?