To cut a long story short, it appears that there is something wrong with the certificate LaCie use in their driver installation, which results in the driver not being installed and the LaCie drive(s) being undetected and unusable by the system.
I suspect this is due to a change in a recent version of Mojave, as reinstalling previous known-good versions of LaCie RAID Manager also fails in the same manner.
Connecting the drive to another Mac that has not had a recent LaCie RAID Manager update works fine, but as of now my production machine is unable to talk to my drive array at all.
I have made LaCie / Seagate aware of the issue.
I suspect this is due to a change in a recent version of Mojave, as reinstalling previous known-good versions of LaCie RAID Manager also fails in the same manner.
Connecting the drive to another Mac that has not had a recent LaCie RAID Manager update works fine, but as of now my production machine is unable to talk to my drive array at all.
I have made LaCie / Seagate aware of the issue.