Precision M6500 will not recognize Intel 530 SSD in second drive bay - worked before with older SSD

Ok problem solvers who love a good challenge,

I'm having issues getting my M6500 to recognize a new Intel 530 SSD in the second drive bay. I have the interposer and bracket installed but the BIOS will not recognize the drive. I have carefully checked that the interposer is plugged onto the drive connectors and that the interposer is seated in the connector on the riser that comes up from the motherboard .

I'm on BIOS A09 and I'm in AHCI mode.

On boot it does not recognize the drive. Hitting F2 for Setup, it only shows my primary drive in the System Information.

Do I need to swap back to RAID in my SATA settings (which I already tried with no luck) and then do something to get the onboard RAID controller to recognize the drive? (this I have not done)

Extra information that may help: I was replacing a Samsung 840 SSD that had been working in the second bay but I was starting to have read issues (In the Event Viewer Application Log I was getting multiple Event ID 51 "An error was detected on device [...] during a paging operation."). So I have had the second bay working before. I even suspect the interposer or riser as a possible problem because one solution to the event ID 51 problem is to replace the SATA "cable". I know the new drive works because I cloned it from the old drive using a USB to SATA connector.

Thanks,
Jack