I've been doing a fair bit of reading on the matter but have hit a few road blocks on the way. To summarize what I'm working with:
*Out of warranty DL380p G8 LFF (12 Bay) with P420i 512mb cache.
*6 x 3TB HGST Raid 5 Array - Has been working for 2 years now without a hitch.
*VMWare Vsphere 6.5.
*Updated P420i firmware to newest 8.32.
*iLO4 updated to 2.61.
My raid firmware was quite out of date until this recent update but with the old 3.x P420i firmware my new 4 x 10TB HGST drives were detecting correctly in the BIOS and also via iLO4, System Inventory, Storage showing the proper size, type, and were authenticating.
Currently when plugged in the eject symbol (LED 3 on the diagram) on the caddy blinks once white and then turns off. So it receives power but that's about it.
I've been reading that 8.32 has been causing issues identifying drives and that 7.02 may be a better route. Downgrading would be my next plan of action to see if I can get these to work. Any input would appreciated.