I was able to resolve this issue and in the event that there is somebody else as ignorant as me, I'm posting my findings.....
Revisited this 6 months later as I now have a second disk shelf (same model ,LSI card and hard drive) running Unraid and have access to SMART data.
When I first bought the disk shelf, I was told I may have trouble with large Seagate drives (I'm running 16tb Exos). The Ebay merchant gave me a handful of SAS interposers to alleviate this. Well, come to find out.... using the interposers means that SMART data won't be available to the controller. So with that knowledge, I removed the SAS interposers, but could not any of the drives to be recognized. Onto the next headache...
After much research into LSI firmware and IOM compatibility, I noticed that my "working" disk shelf was connected via the top IOM. At some point when setting up/purchasing this units I had asked if it mattered which IOM was used and was informed that it did not matter. Well, apparently it does... Connecting to the top IOM made all the drives recognized by the controller and without the SAS interposers. SMART data now available in DSM 7.
I'm sure both of these to the more experienced user are relatively silly errors, but now i know! If anybody would like to explain the more technical reasoning behind either of these, I for one would appreciate it! Thanks