Hp Dl380p G8 Ram Slots

Hi peoples
I have a HP DL380 G8 that currently only has one CPU installed, E2609 V2.
I have purchased a second E-2609 CPU for it along with the additional 2 fans and heatsink but when I install the CPU, the system does not boot.
There is a red light on the server which only clears once the CPU is removed.
I have 2 16 gb slots of memory and balance this with one in each channel A, prior to installing the CPU. I think I am doing it right, but clearly I am missing something. I have tried the CPU in slot 1 and it powers up fine, so it doesnt appear to be a CPU issue.
Any advice is really appreciated,
cheers
Stryder

Dl380p G8 Quickspecs Pdf

Dl380p

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Hp Proliant Dl380p Gen8 Ram Upgrade

  1. One of HP ProLiant DL380p Gen8 running with 80 Gb Ram with Can I use empty memory slots that has been assigned for Processor 2 Depending on the desired configuration, the HPE DL380p Gen8 server can support 8 SFF, 16 SFF, 25 SFF, 8 LFF, or 12 LFF hot plug drive bays. The rest of DIMMs are 8GB modules.
  2. 128GB (16 slots x 8GB@1333MHz) NOTE: HP memory from previous generation servers are not qualified or warranted with this HP ProLiant Server. HP SmartMemory is required to realize the memory performance improvements and enhanced functionality listed in this document for Gen8. For additional information, please see the HP. HP ProLiant DL380p.