LRDIMM combination for 7920

I had put 8 DIMMs of Samsung make part number M386A8K40BM2-CTD6Y in 7920 tower for dual CPU configuration as per UM.

These are 64GB DDP LRDIMM. It did not work.

Tried  the 6 DIMMs configuration for single CPU configuration, that too did not work.

But 16GB RDIMM x 4 of some other make worked for single CPU.

What could be the reason that the combination for the 64GB, both single and dual CPU did not work?

thanks,