Dell precision workstation 7910 Ram compatibility

I recently purchased a Dell t7910 and it was attempting to upgrade the CPUs and RAM. I upgraded the CPUs from one E5 2650 v4 to two xeon E5 2697 V4 and added 4 new sticks of RAM. The current Ram was Micron 8GB 1Rx8 PC4-2400T-RDB-11. I went on eBay and found a lot of 4 Micron 8GB 1Rx8 PC4-2400T-RD1-11 but for some reason they won't work. Is this the wrong type of RAM or is there just something wrong with it? Also any recommendations on what I should upgrade to?